Packet data convergence protocol (PDCP) enhancement for multicast and broadcast services

ABSTRACT

A system, method and apparatus for mobile communications including sidelink transmissions is provided. A user equipment (UE) determines based on a partial sensing resource allocation process associated with a first window size, first radio resources for one or more first sidelink transport blocks. The UE transmits the one or more first sidelink transport blocks based on the first radio resources. The UE receives hybrid automatic repeat request (HARQ) feedback based on a first number of number of negative acknowledgements (NACKs) and a second number of positive acknowledgements (ACKs). Based on application of a threshold, the UE determines second radio resources for one or more second sidelink transport blocks. The UE transmits the one or more second sidelink transport blocks based on the second radio resources.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.63/094,307, entitled “PACKET DATA CONVERGENCE PROTOCOL (PDCP)ENHANCEMENT FOR MULTICAST AND BROADCAST SERVICES”, and filed on Oct. 20,2020. U.S. Provisional Application No. 63/094,307 is incorporated byreference herein.

BACKGROUND

Generally described, computing devices and communication networks can beutilized to exchange information. In a common application, a computingdevice can request/transmit data with another computing device via thecommunication network. More specifically, computing devices may utilizea wireless communication network to exchange information or establishcommunication channels.

Wireless communication networks can include a wide variety of devicesthat include or access components to access a wireless communicationnetwork. Such devices can utilize the wireless communication network tofacilitate interactions with other devices that can access the wirelesscommunication network or to facilitate interaction, through the wirelesscommunication network, with devices utilizing other communicationnetworks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a system of mobile communications accordingto some aspects of some of various exemplary embodiments of the presentdisclosure.

FIG. 2A and FIG. 2B show examples of radio protocol stacks for userplane and control plane, respectively, according to some aspects of someof various exemplary embodiments of the present disclosure.

FIG. 3A, FIG. 3B and FIG. 3C show example mappings between logicalchannels and transport channels in downlink, uplink and sidelink,respectively, according to some aspects of some of various exemplaryembodiments of the present disclosure.

FIG. 4A, FIG. 4B and FIG. 4C show example mappings between transportchannels and physical channels in downlink, uplink and sidelink,respectively, according to some aspects of some of various exemplaryembodiments of the present disclosure.

FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D show examples of radio protocolstacks for NR sidelink communication according to some aspects of someof various exemplary embodiments of the present disclosure.

FIG. 6 shows example physical signals in downlink, uplink and sidelinkaccording to some aspects of some of various exemplary embodiments ofthe present disclosure.

FIG. 7 shows examples of Radio Resource Control (RRC) states andtransitioning between different RRC states according to some aspects ofsome of various exemplary embodiments of the present disclosure.

FIG. 8 shows example frame structure and physical resources according tosome aspects of some of various exemplary embodiments of the presentdisclosure.

FIG. 9 shows example component carrier configurations in differentcarrier aggregation scenarios according to some aspects of some ofvarious exemplary embodiments of the present disclosure.

FIG. 10 shows example bandwidth part configuration and switchingaccording to some aspects of some of various exemplary embodiments ofthe present disclosure.

FIG. 11 shows example four-step contention-based and contention-freerandom access processes according to some aspects of some of variousexemplary embodiments of the present disclosure.

FIG. 12 shows example two-step contention-based and contention-freerandom access processes according to some aspects of some of variousexemplary embodiments of the present disclosure.

FIG. 13 shows example time and frequency structure of SynchronizationSignal and Physical Broadcast Channel (PBCH) Block (SSB) according tosome aspects of some of various exemplary embodiments of the presentdisclosure.

FIG. 14 shows example SSB burst transmissions according to some aspectsof some of various exemplary embodiments of the present disclosure.

FIG. 15 shows example components of a user equipment and a base stationfor transmission and/or reception according to some aspects of some ofvarious exemplary embodiments of the present disclosure.

FIG. 16 shows an example multicast broadcast service (MBS) interestindication according to some aspects of some of various exemplaryembodiments of the present disclosure.

FIG. 17 shows an example packet data convergence protocol (PDCP)duplication process according to some aspects of some of variousexemplary embodiments of the present disclosure.

FIG. 18 shows an example PDCP duplication activation/deactivationsignaling according to some aspects of some of various exemplaryembodiments of the present disclosure.

FIG. 19 shows an example PDCP duplication activation/deactivationsignaling according to some aspects of some of various exemplaryembodiments of the present disclosure.

FIG. 20 shows an example handover process according to some aspects ofsome of various exemplary embodiments of the present disclosure.

FIG. 21A and FIG. 21B show example configurations and processesaccording to some aspects of some of various exemplary embodiments ofthe present disclosure.

FIG. 22 shows an example configuration and process according to someaspects of some of various exemplary embodiments of the presentdisclosure.

FIG. 23 shows an example configuration and process according to someaspects of some of various exemplary embodiments of the presentdisclosure.

FIG. 24 shows an example configuration and process according to someaspects of some of various exemplary embodiments of the presentdisclosure.

DETAILED DESCRIPTION

FIG. 1 shows an example of a system of mobile communications 100according to some aspects of some of various exemplary embodiments ofthe present disclosure. The system of mobile communication 100 may beoperated by a wireless communications system operator such as a MobileNetwork Operator (MNO), a private network operator, a Multiple SystemOperator (MSO), an Internet of Things (JOT) network operator, etc., andmay offer services such as voice, data (e.g., wireless Internet access),messaging, vehicular communications services such as Vehicle toEverything (V2X) communications services, safety services, missioncritical service, services in residential, commercial or industrialsettings such as IoT, industrial IOT (IIOT), etc.

The system of mobile communications 100 may enable various types ofapplications with different requirements in terms of latency,reliability, throughput, etc. Example supported applications includeenhanced Mobile Broadband (eMBB), Ultra-Reliable Low-LatencyCommunications (URLLC), and massive Machine Type Communications (mMTC).eMBB may support stable connections with high peak data rates, as wellas moderate rates for cell-edge users. URLLC may support applicationwith strict requirements in terms of latency and reliability andmoderate requirements in terms of data rate. Example mMTC applicationincludes a network of a massive number of IoT devices, which are onlysporadically active and send small data payloads.

The system of mobile communications 100 may include a Radio AccessNetwork (RAN) portion and a core network portion. The example shown inFIG. 1 illustrates a Next Generation RAN (NG-RAN) 105 and a 5G CoreNetwork (5GC) 110 as examples of the RAN and core network, respectively.Other examples of RAN and core network may be implemented withoutdeparting from the scope of this disclosure. Other examples of RANinclude Evolved Universal Terrestrial Radio Access Network (EUTRAN),Universal Terrestrial Radio Access Network (UTRAN), etc. Other examplesof core network include Evolved Packet Core (EPC), UMTS Core Network(UCN), etc. The RAN implements a Radio Access Technology (RAT) andresides between User Equipments (UEs) 125 and the core network. Examplesof such RATs include New Radio (NR), Long Term Evolution (LTE) alsoknown as Evolved Universal Terrestrial Radio Access (EUTRA), UniversalMobile Telecommunication System (UMTS), etc. The RAT of the examplesystem of mobile communications 100 may be NR. The core network residesbetween the RAN and one or more external networks (e.g., data networks)and is responsible for functions such as mobility management,authentication, session management, setting up bearers and applicationof different Quality of Services (QoSs). The functional layer betweenthe UE 125 and the RAN (e.g., the NG-RAN 105) may be referred to asAccess Stratum (AS) and the functional layer between the UE 125 and thecore network (e.g., the 5GC 110) may be referred to as Non-accessStratum (NAS).

The UEs 125 may include wireless transmission and reception componentsfor communications with one or more nodes in the RAN, one or more relaynodes, or one or more other UEs, etc. Example of UEs include, but arenot limited to, smartphones, tablets, laptops, computers, wirelesstransmission and/or reception units in a vehicle, V2X or Vehicle toVehicle (V2V) devices, wireless sensors, IoT devices, IIOT devices, etc.Other names may be used for UEs such as a Mobile Station (MS), terminalequipment, terminal node, client device, mobile device, etc. Stillfurther, UEs 125 may also include components or subcomponents integratedinto other devices, such as vehicles, to provide wireless communicationfunctionality with nodes in the RAN, other UEs, satellite communicationsas described herein. Such other devices may have other functionality ormultiple functionalities in addition to wireless communications.Accordingly, reference to UE may include the individual componentsfacilitating the wireless communication as well as the entire devicethat incorporates components for facilitating wireless communications.

The RAN may include nodes (e.g., base stations) for communications withthe UEs. For example, the NG-RAN 105 of the system of mobilecommunications 100 may comprise nodes for communications with the UEs125. Different names for the RAN nodes may be used, for exampledepending on the RAT used for the RAN. A RAN node may be referred to asNode B (NB) in a RAN that uses the UMTS RAT. A RAN node may be referredto as an evolved Node B (eNB) in a RAN that uses LTE/EUTRA RAT. For theillustrative example of the system of mobile communications 100 in FIG.1 , the nodes of an NG-RAN 105 may be either a next generation Node B(gNB) 115 or a next generation evolved Node B (ng-eNB) 120. In thisspecification, the terms base station, RAN node, gNB and ng-eNB may beused interchangeably. The gNB 115 may provide NR user plane and controlplane protocol terminations towards the UE 125. The ng-eNB 120 mayprovide E-UTRA user plane and control plane protocol terminationstowards the UE 125. An interface between the gNB 115 and the UE 125 orbetween the ng-eNB 120 and the UE 125 may be referred to as a Uuinterface. The Uu interface may be established with a user planeprotocol stack and a control plane protocol stack. For a Uu interface,the direction from the base station (e.g., the gNB 115 or the ng-eNB120) to the UE 125 may be referred to as downlink and the direction fromthe UE 125 to the base station (e.g., gNB 115 or ng-eNB 120) may bereferred to as uplink.

The gNBs 115 and ng-eNBs 120 may be interconnected with each other bymeans of an Xn interface. The Xn interface may comprise an Xn User plane(Xn-U) interface and an Xn Control plane (Xn-C) interface. The transportnetwork layer of the Xn-U interface may be built on Internet Protocol(IP) transport and GPRS Tunneling Protocol (GTP) may be used on top ofUser Datagram Protocol (UDP)/IP to carry the user plane protocol dataunits (PDUs). Xn-U may provide non-guaranteed delivery of user planePDUs and may support data forwarding and flow control. The transportnetwork layer of the Xn-C interface may be built on Stream ControlTransport Protocol (SCTP) on top of IP. The application layer signalingprotocol may be referred to as XnAP (Xn Application Protocol). The SCTPlayer may provide the guaranteed delivery of application layer messages.In the transport IP layer, point-to-point transmission may be used todeliver the signaling PDUs. The Xn-C interface may support Xn interfacemanagement, UE mobility management, including context transfer and RANpaging, and dual connectivity.

The gNBs 115 and ng-eNBs 120 may also be connected to the 5GC 110 bymeans of the NG interfaces, more specifically to an Access and MobilityManagement Function (AMF) 130 of the 5GC 110 by means of the NG-Cinterface and to a User Plane Function (UPF) 135 of the 5GC 110 by meansof the NG-U interface. The transport network layer of the NG-U interfacemay be built on IP transport and GTP protocol may be used on top ofUDP/IP to carry the user plane PDUs between the NG-RAN node (e.g., gNB115 or ng-eNB 120) and the UPF 135. NG-U may provide non-guaranteeddelivery of user plane PDUs between the NG-RAN node and the UPF. Thetransport network layer of the NG-C interface may be built on IPtransport. For the reliable transport of signaling messages, SCTP may beadded on top of IP. The application layer signaling protocol may bereferred to as NGAP (NG Application Protocol). The SCTP layer mayprovide guaranteed delivery of application layer messages. In thetransport, IP layer point-to-point transmission may be used to deliverthe signaling PDUs. The NG-C interface may provide the followingfunctions: NG interface management; UE context management; UE mobilitymanagement; transport of NAS messages; paging; PDU Session Management;configuration transfer; and warning message transmission.

The gNB 115 or the ng-eNB 120 may host one or more of the followingfunctions: Radio Resource Management functions such as Radio BearerControl, Radio Admission Control, Connection Mobility Control, Dynamicallocation of resources to UEs in both uplink and downlink (e.g.,scheduling); IP and Ethernet header compression, encryption andintegrity protection of data; Selection of an AMF at UE attachment whenno routing to an AMF can be determined from the information provided bythe UE; Routing of User Plane data towards UPF(s); Routing of ControlPlane information towards AMF; Connection setup and release; Schedulingand transmission of paging messages; Scheduling and transmission ofsystem broadcast information (e.g., originated from the AMF);Measurement and measurement reporting configuration for mobility andscheduling; Transport level packet marking in the uplink; SessionManagement; Support of Network Slicing; QoS Flow management and mappingto data radio bearers; Support of UEs in RRC Inactive state;Distribution function for NAS messages; Radio access network sharing;Dual Connectivity; Tight interworking between NR and E-UTRA; andMaintaining security and radio configuration for User Plane 5G system(5GS) Cellular IoT (CIoT) Optimization.

The AMF 130 may host one or more of the following functions: NASsignaling termination; NAS signaling security; AS Security control;Inter CN node signaling for mobility between 3GPP access networks; Idlemode UE Reachability (including control and execution of pagingretransmission); Registration Area management; Support of intra-systemand inter-system mobility; Access Authentication; Access Authorizationincluding check of roaming rights; Mobility management control(subscription and policies); Support of Network Slicing; SessionManagement Function (SMF) selection; Selection of 5GS CIoToptimizations.

The UPF 135 may host one or more of the following functions: Anchorpoint for Intra-/Inter-RAT mobility (when applicable); External PDUsession point of interconnect to Data Network; Packet routing &forwarding; Packet inspection and User plane part of Policy ruleenforcement; Traffic usage reporting; Uplink classifier to supportrouting traffic flows to a data network; Branching point to supportmulti-homed PDU session; QoS handling for user plane, e.g. packetfiltering, gating, UL/DL rate enforcement; Uplink Traffic verification(Service Data Flow (SDF) to QoS flow mapping); Downlink packet bufferingand downlink data notification triggering.

As shown in FIG. 1 , the NG-RAN 105 may support the PC5 interfacebetween two UEs 125 (e.g., UE 125A and UE125B). In the PC5 interface,the direction of communications between two UEs (e.g., from UE 125A toUE 125B or vice versa) may be referred to as sidelink. Sidelinktransmission and reception over the PC5 interface may be supported whenthe UE 125 is inside NG-RAN 105 coverage, irrespective of which RRCstate the UE is in, and when the UE 125 is outside NG-RAN 105 coverage.Support of V2X services via the PC5 interface may be provided by NRsidelink communication and/or V2X sidelink communication.

PC5-S signaling may be used for unicast link establishment with DirectCommunication Request/Accept message. A UE may self-assign its sourceLayer-2 ID for the PC5 unicast link for example based on the V2X servicetype. During unicast link establishment procedure, the UE may send itssource Layer-2 ID for the PC5 unicast link to the peer UE, e.g., the UEfor which a destination ID has been received from the upper layers. Apair of source Layer-2 ID and destination Layer-2 ID may uniquelyidentify a unicast link. The receiving UE may verify that the saiddestination ID belongs to it and may accept the Unicast linkestablishment request from the source UE. During the PC5 unicast linkestablishment procedure, a PC5-RRC procedure on the Access Stratum maybe invoked for the purpose of UE sidelink context establishment as wellas for AS layer configurations, capability exchange etc. PC5-RRCsignaling may enable exchanging UE capabilities and AS layerconfigurations such as Sidelink Radio Bearer configurations between pairof UEs for which a PC5 unicast link is established.

NR sidelink communication may support one of three types of transmissionmodes (e.g., Unicast transmission, Groupcast transmission, and Broadcasttransmission) for a pair of a Source Layer-2 ID and a DestinationLayer-2 ID in the AS. The Unicast transmission mode may be characterizedby: Support of one PC5-RRC connection between peer UEs for the pair;Transmission and reception of control information and user trafficbetween peer UEs in sidelink; Support of sidelink HARQ feedback; Supportof sidelink transmit power control; Support of RLC Acknowledged Mode(AM); and Detection of radio link failure for the PC5-RRC connection.The Groupcast transmission may be characterized by: Transmission andreception of user traffic among UEs belonging to a group in sidelink;and Support of sidelink HARQ feedback. The Broadcast transmission may becharacterized by: Transmission and reception of user traffic among UEsin sidelink.

A Source Layer-2 ID, a Destination Layer-2 ID and a PC5 Link Identifiermay be used for NR sidelink communication. The Source Layer-2 ID may bea link-layer identity that identifies a device or a group of devicesthat are recipients of sidelink communication frames. The DestinationLayer-2 ID may be a link-layer identity that identifies a device thatoriginates sidelink communication frames. In some examples, the SourceLayer-2 ID and the Destination Layer-2 ID may be assigned by amanagement function in the Core Network. The Source Layer-2 ID mayidentify the sender of the data in NR sidelink communication. The SourceLayer-2 ID may be 24 bits long and may be split in the MAC layer intotwo bit strings: One bit string may be the LSB part (8 bits) of SourceLayer-2 ID and forwarded to physical layer of the sender. This mayidentify the source of the intended data in sidelink control informationand may be used for filtering of packets at the physical layer of thereceiver; and the Second bit string may be the MSB part (16 bits) of theSource Layer-2 ID and may be carried within the Medium Access Control(MAC) header. This may be used for filtering of packets at the MAC layerof the receiver. The Destination Layer-2 ID may identify the target ofthe data in NR sidelink communication. For NR sidelink communication,the Destination Layer-2 ID may be 24 bits long and may be split in theMAC layer into two bit strings: One bit string may be the LSB part (16bits) of Destination Layer-2 ID and forwarded to physical layer of thesender. This may identify the target of the intended data in sidelinkcontrol information and may be used for filtering of packets at thephysical layer of the receiver; and the Second bit string may be the MSBpart (8 bits) of the Destination Layer-2 ID and may be carried withinthe MAC header. This may be used for filtering of packets at the MAClayer of the receiver. The PC5 Link Identifier may uniquely identify thePC5 unicast link in a UE for the lifetime of the PC5 unicast link. ThePC5 Link Identifier may be used to indicate the PC5 unicast link whosesidelink Radio Link failure (RLF) declaration was made and PC5-RRCconnection was released.

FIG. 2A and FIG. 2B show examples of radio protocol stacks for userplane and control plane, respectively, according to some aspects of someof various exemplary embodiments of the present disclosure. As shown inFIG. 2A, the protocol stack for the user plane of the Uu interface(between the UE 125 and the gNB 115) includes Service Data AdaptationProtocol (SDAP) 201 and SDAP 211, Packet Data Convergence Protocol(PDCP) 202 and PDCP 212, Radio Link Control (RLC) 203 and RLC 213, MAC204 and MAC 214 sublayers of layer 2 and Physical (PHY) 205 and PHY 215layer (layer 1 also referred to as L1).

The PHY 205 and PHY 215 offer transport channels 244 to the MAC 204 andMAC 214 sublayer. The MAC 204 and MAC 214 sublayer offer logicalchannels 243 to the RLC 203 and RLC 213 sublayer. The RLC 203 and RLC213 sublayer offer RLC channels 242 to the PDCP 202 and PCP 212sublayer. The PDCP 202 and PDCP 212 sublayer offer radio bearers 241 tothe SDAP 201 and SDAP 211 sublayer. Radio bearers may be categorizedinto two groups: Data Radio Bearers (DRBs) for user plane data andSignaling Radio Bearers (SRBs) for control plane data. The SDAP 201 andSDAP 211 sublayer offers QoS flows 240 to 5GC.

The main services and functions of the MAC 204 or MAC 214 sublayerinclude: mapping between logical channels and transport channels;Multiplexing/demultiplexing of MAC Service Data Units (SDUs) belongingto one or different logical channels into/from Transport Blocks (TB)delivered to/from the physical layer on transport channels; Schedulinginformation reporting; Error correction through Hybrid Automatic RepeatRequest (HARQ) (one HARQ entity per cell in case of carrier aggregation(CA)); Priority handling between UEs by means of dynamic scheduling;Priority handling between logical channels of one UE by means of LogicalChannel Prioritization (LCP); Priority handling between overlappingresources of one UE; and Padding. A single MAC entity may supportmultiple numerologies, transmission timings and cells. Mappingrestrictions in logical channel prioritization control whichnumerology(ies), cell(s), and transmission timing(s) a logical channelmay use.

The HARQ functionality may ensure delivery between peer entities atLayer 1. A single HARQ process may support one TB when the physicallayer is not configured for downlink/uplink spatial multiplexing, andwhen the physical layer is configured for downlink/uplink spatialmultiplexing, a single HARQ process may support one or multiple TBs.

The RLC 203 or RLC 213 sublayer may support three transmission modes:Transparent Mode (TM); Unacknowledged Mode (UM); and Acknowledged Mode(AM). The RLC configuration may be per logical channel with nodependency on numerologies and/or transmission durations, and AutomaticRepeat Request (ARQ) may operate on any of the numerologies and/ortransmission durations the logical channel is configured with.

The main services and functions of the RLC 203 or RLC 213 sublayerdepend on the transmission mode (e.g., TM, UM or AM) and may include:Transfer of upper layer PDUs; Sequence numbering independent of the onein PDCP (UM and AM); Error Correction through ARQ (AM only);Segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs;Reassembly of SDU (AM and UM); Duplicate Detection (AM only); RLC SDUdiscard (AM and UM); RLC re-establishment; and Protocol error detection(AM only).

The automatic repeat request within the RLC 203 or RLC 213 sublayer mayhave the following characteristics: ARQ retransmits RLC SDUs or RLC SDUsegments based on RLC status reports; Polling for RLC status report maybe used when needed by RLC; RLC receiver may also trigger RLC statusreport after detecting a missing RLC SDU or RLC SDU segment.

The main services and functions of the PDCP 202 or PDCP 212 sublayer mayinclude: Transfer of data (user plane or control plane); Maintenance ofPDCP Sequence Numbers (SNs); Header compression and decompression usingthe Robust Header Compression (ROHC) protocol; Header compression anddecompression using EHC protocol; Ciphering and deciphering; Integrityprotection and integrity verification; Timer based SDU discard; Routingfor split bearers; Duplication; Reordering and in-order delivery;Out-of-order delivery; and Duplicate discarding.

The main services and functions of SDAP 201 or SDAP 211 include: Mappingbetween a QoS flow and a data radio bearer; and Marking QoS Flow ID(QFI) in both downlink and uplink packets. A single protocol entity ofSDAP may be configured for each individual PDU session.

As shown in FIG. 2B, the protocol stack of the control plane of the Uuinterface (between the UE 125 and the gNB 115) includes PHY layer (layer1), and MAC, RLC and PDCP sublayers of layer 2 as described above and inaddition, the RRC 206 sublayer and RRC 216 sublayer. The main servicesand functions of the RRC 206 sublayer and the RRC 216 sublayer over theUu interface include: Broadcast of System Information related to AS andNAS; Paging initiated by 5GC or NG-RAN; Establishment, maintenance andrelease of an RRC connection between the UE and NG-RAN (includingAddition, modification and release of carrier aggregation; and Addition,modification and release of Dual Connectivity in NR or between E-UTRAand NR); Security functions including key management; Establishment,configuration, maintenance and release of SRBs and DRBs; Mobilityfunctions (including Handover and context transfer; UE cell selectionand reselection and control of cell selection and reselection; andInter-RAT mobility); QoS management functions; UE measurement reportingand control of the reporting; Detection of and recovery from radio linkfailure; and NAS message transfer to/from NAS from/to UE. The NAS 207and NAS 227 layer is a control protocol (terminated in AMF on thenetwork side) that performs the functions such as authentication,mobility management, security control, etc.

The sidelink specific services and functions of the RRC sublayer overthe Uu interface include: Configuration of sidelink resource allocationvia system information or dedicated signaling; Reporting of UE sidelinkinformation; Measurement configuration and reporting related tosidelink; and Reporting of UE assistance information for SL trafficpattern(s).

FIG. 3A, FIG. 3B and FIG. 3C show example mappings between logicalchannels and transport channels in downlink, uplink and sidelink,respectively, according to some aspects of some of various exemplaryembodiments of the present disclosure. Different kinds of data transferservices may be offered by MAC. Each logical channel type may be definedby what type of information is transferred. Logical channels may beclassified into two groups: Control Channels and Traffic Channels.Control channels may be used for the transfer of control planeinformation only. The Broadcast Control Channel (BCCH) is a downlinkchannel for broadcasting system control information. The Paging ControlChannel (PCCH) is a downlink channel that carries paging messages. TheCommon Control Channel (CCCH) is channel for transmitting controlinformation between UEs and network. This channel may be used for UEshaving no RRC connection with the network. The Dedicated Control Channel(DCCH) is a point-to-point bi-directional channel that transmitsdedicated control information between a UE and the network and may beused by UEs having an RRC connection. Traffic channels may be used forthe transfer of user plane information only. The Dedicated TrafficChannel (DTCH) is a point-to-point channel, dedicated to one UE, for thetransfer of user information. A DTCH may exist in both uplink anddownlink. Sidelink Control Channel (SCCH) is a sidelink channel fortransmitting control information (e.g., PC5-RRC and PC5-S messages) fromone UE to other UE(s). Sidelink Traffic Channel (STCH) is a sidelinkchannel for transmitting user information from one UE to other UE(s).Sidelink Broadcast Control Channel (SBCCH) is a sidelink channel forbroadcasting sidelink system information from one UE to other UE(s).

The downlink transport channel types include Broadcast Channel (BCH),Downlink Shared Channel (DL-SCH), and Paging Channel (PCH). The BCH maybe characterized by: fixed, pre-defined transport format; andrequirement to be broadcast in the entire coverage area of the cell,either as a single message or by beamforming different BCH instances.The DL-SCH may be characterized by: support for HARQ; support fordynamic link adaptation by varying the modulation, coding and transmitpower; possibility to be broadcast in the entire cell; possibility touse beamforming; support for both dynamic and semi-static resourceallocation; and the support for UE Discontinuous Reception (DRX) toenable UE power saving. The DL-SCH may be characterized by: support forHARQ; support for dynamic link adaptation by varying the modulation,coding and transmit power; possibility to be broadcast in the entirecell; possibility to use beamforming; support for both dynamic andsemi-static resource allocation; support for UE discontinuous reception(DRX) to enable UE power saving. The PCH may be characterized by:support for UE discontinuous reception (DRX) to enable UE power saving(DRX cycle is indicated by the network to the UE); requirement to bebroadcast in the entire coverage area of the cell, either as a singlemessage or by beamforming different BCH instances; mapped to physicalresources which can be used dynamically also for traffic/other controlchannels.

In downlink, the following connections between logical channels andtransport channels may exist: BCCH may be mapped to BCH; BCCH may bemapped to DL-SCH; PCCH may be mapped to PCH; CCCH may be mapped toDL-SCH; DCCH may be mapped to DL-SCH; and DTCH may be mapped to DL-SCH.

The uplink transport channel types include Uplink Shared Channel(UL-SCH) and Random Access Channel(s) (RACH). The UL-SCH may becharacterized by possibility to use beamforming; support for dynamiclink adaptation by varying the transmit power and potentially modulationand coding; support for HARQ; support for both dynamic and semi-staticresource allocation. The RACH may be characterized by limited controlinformation; and collision risk.

In Uplink, the following connections between logical channels andtransport channels may exist: CCCH may be mapped to UL-SCH; DCCH may bemapped to UL-SCH; and DTCH may be mapped to UL-SCH.

The sidelink transport channel types include: Sidelink broadcast channel(SL-BCH) and Sidelink shared channel (SL-SCH). The SL-BCH may becharacterized by pre-defined transport format. The SL-SCH may becharacterized by support for unicast transmission, groupcasttransmission and broadcast transmission; support for both UE autonomousresource selection and scheduled resource allocation by NG-RAN; supportfor both dynamic and semi-static resource allocation when UE isallocated resources by the NG-RAN; support for HARQ; and support fordynamic link adaptation by varying the transmit power, modulation andcoding.

In the sidelink, the following connections between logical channels andtransport channels may exist: SCCH may be mapped to SL-SCH; STCH may bemapped to SL-SCH; and SBCCH may be mapped to SL-BCH.

FIG. 4A, FIG. 4B and FIG. 4C show example mappings between transportchannels and physical channels in downlink, uplink and sidelink,respectively, according to some aspects of some of various exemplaryembodiments of the present disclosure. The physical channels in downlinkinclude Physical Downlink Shared Channel (PDSCH), Physical DownlinkControl Channel (PDCCH) and Physical Broadcast Channel (PBCH). The PCHand DL-SCH transport channels are mapped to the PDSCH. The BCH transportchannel is mapped to the PBCH. A transport channel is not mapped to thePDCCH but Downlink Control Information (DCI) is transmitted via thePDCCH.

The physical channels in the uplink include Physical Uplink SharedChannel (PUSCH), Physical Uplink Control Channel (PUCCH) and PhysicalRandom Access Channel (PRACH). The UL-SCH transport channel may bemapped to the PUSCH and the RACH transport channel may be mapped to thePRACH. A transport channel is not mapped to the PUCCH but Uplink ControlInformation (UCI) is transmitted via the PUCCH.

The physical channels in the sidelink include Physical Sidelink SharedChannel (PSSCH), Physical Sidelink Control Channel (PSCCH), PhysicalSidelink Feedback Channel (PSFCH) and Physical Sidelink BroadcastChannel (PSBCH). The Physical Sidelink Control Channel (PSCCH) mayindicate resource and other transmission parameters used by a UE forPSSCH. The Physical Sidelink Shared Channel (PSSCH) may transmit the TBsof data themselves, and control information for HARQ procedures and CSIfeedback triggers, etc. At least 6 OFDM symbols within a slot may beused for PSSCH transmission. Physical Sidelink Feedback Channel (PSFCH)may carry the HARQ feedback over the sidelink from a UE which is anintended recipient of a PSSCH transmission to the UE which performed thetransmission. PSFCH sequence may be transmitted in one PRB repeated overtwo OFDM symbols near the end of the sidelink resource in a slot. TheSL-SCH transport channel may be mapped to the PSSCH. The SL-BCH may bemapped to PSBCH. No transport channel is mapped to the PSFCH butSidelink Feedback Control Information (SFCI) may be mapped to the PSFCH.No transport channel is mapped to PSCCH but Sidelink Control Information(SCI) may mapped to the PSCCH.

FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D show examples of radio protocolstacks for NR sidelink communication according to some aspects of someof various exemplary embodiments of the present disclosure. The ASprotocol stack for user plane in the PC5 interface (i.e., for STCH) mayconsist of SDAP, PDCP, RLC and MAC sublayers, and the physical layer.The protocol stack of user plane is shown in FIG. 5A. The AS protocolstack for SBCCH in the PC5 interface may consist of RRC, RLC, MACsublayers, and the physical layer as shown below in FIG. 5B. For supportof PC5-S protocol, PC5-S is located on top of PDCP, RLC and MACsublayers, and the physical layer in the control plane protocol stackfor SCCH for PC5-S, as shown in FIG. 5C. The AS protocol stack for thecontrol plane for SCCH for RRC in the PC5 interface consists of RRC,PDCP, RLC and MAC sublayers, and the physical layer. The protocol stackof control plane for SCCH for RRC is shown in FIG. 5D.

The Sidelink Radio Bearers (SLRBs) may be categorized into two groups:Sidelink Data Radio Bearers (SL DRB) for user plane data and SidelinkSignaling Radio Bearers (SL SRB) for control plane data. Separate SLSRBs using different SCCHs may be configured for PC5-RRC and PC5-Ssignaling, respectively.

The MAC sublayer may provide the following services and functions overthe PC5 interface: Radio resource selection; Packet filtering; Priorityhandling between uplink and sidelink transmissions for a given UE; andSidelink CSI reporting. With logical channel prioritization restrictionsin MAC, only sidelink logical channels belonging to the same destinationmay be multiplexed into a MAC PDU for every unicast, groupcast andbroadcast transmission which may be associated to the destination. Forpacket filtering, a SL-SCH MAC header including portions of both SourceLayer-2 ID and a Destination Layer-2 ID may be added to a MAC PDU. TheLogical Channel Identifier (LCID) included within a MAC subheader mayuniquely identify a logical channel within the scope of the SourceLayer-2 ID and Destination Layer-2 ID combination.

The services and functions of the RLC sublayer may be supported forsidelink. Both RLC Unacknowledged Mode (UM) and Acknowledged Mode (AM)may be used in unicast transmission while only UM may be used ingroupcast or broadcast transmission. For UM, only unidirectionaltransmission may be supported for groupcast and broadcast.

The services and functions of the PDCP sublayer for the Uu interface maybe supported for sidelink with some restrictions: Out-of-order deliverymay be supported only for unicast transmission; and Duplication may notbe supported over the PC5 interface.

The SDAP sublayer may provide the following service and function overthe PC5 interface: Mapping between a QoS flow and a sidelink data radiobearer. There may be one SDAP entity per destination for one of unicast,groupcast and broadcast which is associated to the destination.

The RRC sublayer may provide the following services and functions overthe PC5 interface: Transfer of a PC5-RRC message between peer UEs;Maintenance and release of a PC5-RRC connection between two UEs; andDetection of sidelink radio link failure for a PC5-RRC connection basedon indication from MAC or RLC. A PC5-RRC connection may be a logicalconnection between two UEs for a pair of Source and Destination Layer-2IDs which may be considered to be established after a corresponding PC5unicast link is established. There may be one-to-one correspondencebetween the PC5-RRC connection and the PC5 unicast link. A UE may havemultiple PC5-RRC connections with one or more UEs for different pairs ofSource and Destination Layer-2 IDs. Separate PC5-RRC procedures andmessages may be used for a UE to transfer UE capability and sidelinkconfiguration including SL-DRB configuration to the peer UE. Both peerUEs may exchange their own UE capability and sidelink configurationusing separate bi-directional procedures in both sidelink directions.

FIG. 6 shows example physical signals in downlink, uplink and sidelinkaccording to some aspects of some of various exemplary embodiments ofthe present disclosure. The Demodulation Reference Signal (DM-RS) may beused in downlink, uplink and sidelink and may be used for channelestimation. DM-RS is a UE-specific reference signal and may betransmitted together with a physical channel in downlink, uplink orsidelink and may be used for channel estimation and coherent detectionof the physical channel. The Phase Tracking Reference Signal (PT-RS) maybe used in downlink, uplink and sidelink and may be used for trackingthe phase and mitigating the performance loss due to phase noise. ThePT-RS may be used mainly to estimate and minimize the effect of CommonPhase Error (CPE) on system performance. Due to the phase noiseproperties, PT-RS signal may have a low density in the frequency domainand a high density in the time domain. PT-RS may occur in combinationwith DM-RS and when the network has configured PT-RS to be present. ThePositioning Reference Signal (PRS) may be used in downlink forpositioning using different positioning techniques. PRS may be used tomeasure the delays of the downlink transmissions by correlating thereceived signal from the base station with a local replica in thereceiver. The Channel State Information Reference Signal (CSI-RS) may beused in downlink and sidelink. CSI-RS may be used for channel stateestimation, Reference Signal Received Power (RSRP) measurement formobility and beam management, time/frequency tracking for demodulationamong other uses. CSI-RS may be configured UE-specifically but multipleusers may share the same CSI-RS resource. The UE may determine CSIreports and transit them in the uplink to the base station using PUCCHor PUSCH. The CSI report may be carried in a sidelink MAC CE. ThePrimary Synchronization Signal (PSS) and the Secondary SynchronizationSignal (SSS) may be used for radio fame synchronization. The PSS and SSSmay be used for the cell search procedure during the initial attach orfor mobility purposes. The Sounding Reference Signal (SRS) may be usedin uplink for uplink channel estimation. Similar to CSI-RS, the SRS mayserve as QCL reference for other physical channels such that they can beconfigured and transmitted quasi-collocated with SRS. The Sidelink PSS(S-PSS) and Sidelink SSS (S-SSS) may be used in sidelink for sidelinksynchronization.

FIG. 7 shows examples of Radio Resource Control (RRC) states andtransitioning between different RRC states according to some aspects ofsome of various exemplary embodiments of the present disclosure. A UEmay be in one of three RRC states: RRC Connected State 710, RRC IdleState 720 and RRC Inactive state 730. After power up, the UE may be inRRC Idle state 720 and the UE may establish connection with the networkusing initial access and via an RRC connection establishment procedureto perform data transfer and/or to make/receive voice calls. Once RRCconnection is established, the UE may be in RRC Connected State 710. TheUE may transition from the RRC Idle state 720 to the RRC connected state710 or from the RRC Connected State 710 to the RRC Idle state 720 usingthe RRC connection Establishment/Release procedures 740.

To reduce the signaling load and the latency resulting from frequenttransitioning from the RRC Connected State 710 to the RRC Idle State 720when the UE transmits frequent small data, the RRC Inactive State 730may be used. In the RRC Inactive State 730, the AS context may be storedby both UE and gNB. This may result in faster state transition from theRRC Inactive State 730 to RRC Connected State 710. The UE may transitionfrom the RRC Inactive State 730 to the RRC Connected State 710 or fromthe RRC Connected State 710 to the RRC Inactive State 730 using the RRCConnection Resume/Inactivation procedures 760. The UE may transitionfrom the RRC Inactive State 730 to RRC Idle State 720 using an RRCConnection Release procedure 750.

FIG. 8 shows example frame structure and physical resources according tosome aspects of some of various exemplary embodiments of the presentdisclosure. The downlink or uplink or sidelink transmissions may beorganized into frames with 10 ms duration, consisting of ten 1 mssubframes. Each subframe may consist of 1, 2, 4, . . . slots, whereinthe number of slots per subframe may depend of the subcarrier spacing ofthe carrier on which the transmission takes place. The slot duration maybe 14 symbols with Normal Cyclic Prefix (CP) and 12 symbols withExtended CP and may scale in time as a function of the used sub-carrierspacing so that there is an integer number of slots in a subframe. FIG.8 shows a resource grid in time and frequency domain. Each element ofthe resource grid, comprising one symbol in time and one subcarrier infrequency, is referred to as a Resource Element (RE). A Resource Block(RB) may be defined as 12 consecutive subcarriers in the frequencydomain.

In some examples and with non-slot-based scheduling, the transmission ofa packet may occur over a portion of a slot, for example during 2, 4 or7 OFDM symbols which may also be referred to as mini-slots. Themini-slots may be used for low latency applications such as URLLC andoperation in unlicensed bands. In some embodiments, the mini-slots mayalso be used for fast flexible scheduling of services (e.g., pre-emptionof URLLC over eMBB).

FIG. 9 shows example component carrier configurations in differentcarrier aggregation scenarios according to some aspects of some ofvarious exemplary embodiments of the present disclosure. In CarrierAggregation (CA), two or more Component Carriers (CCs) may beaggregated. A UE may simultaneously receive or transmit on one ormultiple CCs depending on its capabilities. CA may be supported for bothcontiguous and non-contiguous CCs in the same band or on different bandsas shown in FIG. 9 . A gNB and the UE may communicate using a servingcell. A serving cell may be associated at least with one downlink CC(e.g., may be associated only with one downlink CC or may be associatedwith a downlink CC and an uplink CC). A serving cell may be a PrimaryCell (PCell) or a Secondary cCell (SCell).

A UE may adjust the timing of its uplink transmissions using an uplinktiming control procedure. A Timing Advance (TA) may be used to adjustthe uplink frame timing relative to the downlink frame timing. The gNBmay determine the desired Timing Advance setting and provides that tothe UE. The UE may use the provided TA to determine its uplink transmittiming relative to the UE's observed downlink receive timing.

In the RRC Connected state, the gNB may be responsible for maintainingthe timing advance to keep the L1 synchronized. Serving cells havinguplink to which the same timing advance applies and using the sametiming reference cell are grouped in a Timing Advance Group (TAG). A TAGmay contain at least one serving cell with configured uplink. Themapping of a serving cell to a TAG may be configured by RRC. For theprimary TAG, the UE may use the PCell as timing reference cell, exceptwith shared spectrum channel access where an SCell may also be used astiming reference cell in certain cases. In a secondary TAG, the UE mayuse any of the activated SCells of this TAG as a timing reference celland may not change it unless necessary.

Timing advance updates may be signaled by the gNB to the UE via MAC CEcommands. Such commands may restart a TAG-specific timer which mayindicate whether the L1 can be synchronized or not: when the timer isrunning, the L1 may be considered synchronized, otherwise, the L1 may beconsidered non-synchronized (in which case uplink transmission may onlytake place on PRACH).

A UE with single timing advance capability for CA may simultaneouslyreceive and/or transmit on multiple CCs corresponding to multipleserving cells sharing the same timing advance (multiple serving cellsgrouped in one TAG). A UE with multiple timing advance capability for CAmay simultaneously receive and/or transmit on multiple CCs correspondingto multiple serving cells with different timing advances (multipleserving cells grouped in multiple TAGs). The NG-RAN may ensure that eachTAG contains at least one serving cell. A non-CA capable UE may receiveon a single CC and may transmit on a single CC corresponding to oneserving cell only (one serving cell in one TAG).

The multi-carrier nature of the physical layer in case of CA may beexposed to the MAC layer and one HARQ entity may be required per servingcell. When CA is configured, the UE may have one RRC connection with thenetwork. At RRC connection establishment/re-establishment/handover, oneserving cell (e.g., the PCell) may provide the NAS mobility information.Depending on UE capabilities, SCells may be configured to form togetherwith the PCell a set of serving cells. The configured set of servingcells for a UE may consist of one PCell and one or more SCells. Thereconfiguration, addition and removal of SCells may be performed by RRC.

In a dual connectivity scenario, a UE may be configured with a pluralityof cells comprising a Master Cell Group (MCG) for communications with amaster base station, a Secondary Cell Group (SCG) for communicationswith a secondary base station, and two MAC entities: one MAC entity andfor the MCG for communications with the master base station and one MACentity for the SCG for communications with the secondary base station.

FIG. 10 shows example bandwidth part configuration and switchingaccording to some aspects of some of various exemplary embodiments ofthe present disclosure. The UE may be configured with one or moreBandwidth Parts (BWPs) 1010 on a given component carrier. In someexamples, one of the one or more bandwidth parts may be active at atime. The active bandwidth part may define the UE's operating bandwidthwithin the cell's operating bandwidth. For initial access, and until theUE's configuration in a cell is received, initial bandwidth part 1020determined from system information may be used. With BandwidthAdaptation (BA), for example through BWP switching 1040, the receive andtransmit bandwidth of a UE may not be as large as the bandwidth of thecell and may be adjusted. For example, the width may be ordered tochange (e.g. to shrink during period of low activity to save power); thelocation may move in the frequency domain (e.g. to increase schedulingflexibility); and the subcarrier spacing may be ordered to change (e.g.to allow different services). The first active BWP 1020 may be theactive BWP upon RRC (re-) configuration for a PCell or activation of anSCell.

For a downlink BWP or uplink BWP in a set of downlink BWPs or uplinkBWPs, respectively, the UE may be provided the following configurationparameters: a Subcarrier Spacing (SCS); a cyclic prefix; a common RB anda number of contiguous RBs; an index in the set of downlink BWPs oruplink BWPs by respective BWP-Id; a set of BWP-common and a set ofBWP-dedicated parameters. A BWP may be associated with an OFDMnumerology according to the configured subcarrier spacing and cyclicprefix for the BWP. For a serving cell, a UE may be provided by adefault downlink BWP among the configured downlink BWPs. If a UE is notprovided a default downlink BWP, the default downlink BWP may be theinitial downlink BWP.

A downlink BWP may be associated with a BWP inactivity timer. If the BWPinactivity timer associated with the active downlink BWP expires and ifthe default downlink BWP is configured, the UE may perform BWP switchingto the default BWP. If the BWP inactivity timer associated with theactive downlink BWP expires and if the default downlink BWP is notconfigured, the UE may perform BWP switching to the initial downlinkBWP.

FIG. 11 shows example four-step contention-based and contention-freerandom access processes according to some aspects of some of variousexemplary embodiments of the present disclosure. FIG. 12 shows exampletwo-step contention-based and contention-free random access processesaccording to some aspects of some of various exemplary embodiments ofthe present disclosure. The random access procedure may be triggered bya number of events, for example: Initial access from RRC Idle State; RRCConnection Re-establishment procedure; downlink or uplink data arrivalduring RRC Connected State when uplink synchronization status is“non-synchronized”; uplink data arrival during RRC Connected State whenthere are no PUCCH resources for Scheduling Request (SR) available; SRfailure; Request by RRC upon synchronous reconfiguration (e.g.handover); Transition from RRC Inactive State; to establish timealignment for a secondary TAG; Request for Other System Information(SI); Beam Failure Recovery (BFR); Consistent uplink Listen-Before-Talk(LBT) failure on PCell.

Two types of Random Access (RA) procedure may be supported: 4-step RAtype with MSG1 and 2-step RA type with MSGA. Both types of RA proceduremay support Contention-Based Random Access (CBRA) and Contention-FreeRandom Access (CFRA) as shown in FIG. 11 and FIG. 12 .

The UE may select the type of random access at initiation of the randomaccess procedure based on network configuration. When CFRA resources arenot configured, a RSRP threshold may be used by the UE to select between2-step RA type and 4-step RA type. When CFRA resources for 4-step RAtype are configured, UE may perform random access with 4-step RA type.When CFRA resources for 2-step RA type are configured, UE may performrandom access with 2-step RA type.

The MSG1 of the 4-step RA type may consist of a preamble on PRACH. AfterMSG1 transmission, the UE may monitor for a response from the networkwithin a configured window. For CFRA, dedicated preamble for MSG1transmission may be assigned by the network and upon receiving RandomAccess Response (RAR) from the network, the UE may end the random accessprocedure as shown in FIG. 11 . For CBRA, upon reception of the randomaccess response, the UE may send MSG3 using the uplink grant scheduledin the random access response and may monitor contention resolution asshown in FIG. 11 . If contention resolution is not successful after MSG3(re)transmission(s), the UE may go back to MSG1 transmission.

The MSGA of the 2-step RA type may include a preamble on PRACH and apayload on PUSCH. After MSGA transmission, the UE may monitor for aresponse from the network within a configured window. For CFRA,dedicated preamble and PUSCH resource may be configured for MSGAtransmission and upon receiving the network response, the UE may end therandom access procedure as shown in FIG. 12 . For CBRA, if contentionresolution is successful upon receiving the network response, the UE mayend the random access procedure as shown in FIG. 12 ; while if fallbackindication is received in MSGB, the UE may perform MSG3 transmissionusing the uplink grant scheduled in the fallback indication and maymonitor contention resolution. If contention resolution is notsuccessful after MSG3 (re)transmission(s), the UE may go back to MSGAtransmission.

FIG. 13 shows example time and frequency structure of SynchronizationSignal and Physical Broadcast Channel (PBCH) Block (SSB) according tosome aspects of some of various exemplary embodiments of the presentdisclosure. The SS/PBCH Block (SSB) may consist of Primary and SecondarySynchronization Signals (PSS, SSS), each occupying 1 symbol and 127subcarriers (e.g., subcarrier numbers 56 to 182 in FIG. 13 ), and PBCHspanning across 3 OFDM symbols and 240 subcarriers, but on one symbolleaving an unused part in the middle for SSS as show in FIG. 13 . Thepossible time locations of SSBs within a half-frame may be determined bysub-carrier spacing and the periodicity of the half-frames, where SSBsare transmitted, may be configured by the network. During a half-frame,different SSBs may be transmitted in different spatial directions (i.e.using different beams, spanning the coverage area of a cell).

The PBCH may be used to carry Master Information Block (MIB) used by aUE during cell search and initial access procedures. The UE may firstdecode PBCH/MIB to receive other system information. The MIB may providethe UE with parameters required to acquire System Information Block 1(SIB1), more specifically, information required for monitoring of PDCCHfor scheduling PDSCH that carries SIB1. In addition, MIB may indicatecell barred status information. The MIB and SIB1 may be collectivelyreferred to as the minimum system information (SI) and SIB1 may bereferred to as remaining minimum system information (RMSI). The othersystem information blocks (SIBS) (e.g., SIB2, SIB3, . . . , SIB10 andSIBpos) may be referred to as Other SI. The Other SI may be periodicallybroadcast on DL-SCH, broadcast on-demand on DL-SCH (e.g., upon requestfrom UEs in RRC Idle State, RRC Inactive State, or RRC connected State),or sent in a dedicated manner on DL-SCH to UEs in RRC Connected State(e.g., upon request, if configured by the network, from UEs in RRCConnected State or when the UE has an active BWP with no common searchspace configured).

FIG. 14 shows example SSB burst transmissions according to some aspectsof some of various exemplary embodiments of the present disclosure. AnSSB burst may include N SSBs and each SSB of the N SSBs may correspondto a beam. The SSB bursts may be transmitted according to a periodicity(e.g., SSB burst period). During a contention-based random accessprocess, a UE may perform a random access resource selection process,wherein the UE first selects an SSB before selecting a RA preamble. TheUE may select an SSB with an RSRP above a configured threshold value. Insome embodiments, the UE may select any SSB if no SSB with RSRP abovethe configured threshold is available. A set of random access preamblesmay be associated with an SSB. After selecting an SSB, the UE may selecta random access preamble from the set of random access preamblesassociated with the SSB and may transmit the selected random accesspreamble to start the random access process.

In some embodiments, a beam of the N beams may be associated with aCSI-RS resource. A UE may measure CSI-RS resources and may select aCSI-RS with RSRP above a configured threshold value. The UE may select arandom access preamble corresponding to the selected CSI-RS and maytransmit the selected random access process to start the random accessprocess. If there is no random access preamble associated with theselected CSI-RS, the UE may select a random access preamblecorresponding to an SSB which is Quasi-Collocated with the selectedCSI-RS.

In some embodiments, based on the UE measurements of the CSI-RSresources and the UE CSI reporting, the base station may determine aTransmission Configuration Indication (TCI) state and may indicate theTCI state to the UE, wherein the UE may use the indicated TCI state forreception of downlink control information (e.g., via PDCCH) or data(e.g., via PDSCH). The UE may use the indicated TCI state for using theappropriate beam for reception of data or control information. Theindication of the TCI states may be using RRC configuration or incombination of RRC signaling and dynamic signaling (e.g., via a MACControl element (MAC CE) and/or based on a value of field in thedownlink control information that schedules the downlink transmission).The TCI state may indicate a Quasi-Colocation (QCL) relationship betweena downlink reference signal such as CSI-RS and the DM-RS associated withthe downlink control or data channels (e.g., PDCCH or PDSCH,respectively).

In some embodiments, the UE may be configured with a list of up to MTCI-State configurations, using Physical Downlink Shared Channel (PDSCH)configuration parameters, to decode PDSCH according to a detected PDCCHwith DCI intended for the UE and the given serving cell, where M maydepends on the UE capability. Each TCI-State may contain parameters forconfiguring a QCL relationship between one or two downlink referencesignals and the DM-RS ports of the PDSCH, the DM-RS port of PDCCH or theCSI-RS port(s) of a CSI-RS resource. The quasi co-location relationshipmay be configured by one or more RRC parameters. The quasi co-locationtypes corresponding to each DL RS may take one of the following values:‘QCL-TypeA’: {Doppler shift, Doppler spread, average delay, delayspread}; ‘QCL-TypeB’: {Doppler shift, Doppler spread}; ‘QCL-TypeC’:{Doppler shift, average delay}; ‘QCL-TypeD’: {Spatial Rx parameter}. TheUE may receive an activation command (e.g., a MAC CE), used to map TCIstates to the codepoints of a DCI field.

FIG. 15 shows example components of a user equipment and a base stationfor transmission and/or reception according to some aspects of some ofvarious exemplary embodiments of the present disclosure. In oneembodiment, the illustrative components of FIG. 15 may be considered tobe illustrative of functional blocks of an illustrative base station1505. In another embodiment, the illustrative components of FIG. 15 maybe considered to be illustrative of functional blocks of an illustrativeuser equipment 1500. Accordingly, the components illustrated in FIG. 15are not necessarily limited to either a user equipment or base station.

Antenna 1510 may comprise one or more antenna elements and may enabledifferent input-output antenna configurations including Multiple-InputMultiple Output (MIMO) configuration, Multiple-Input Single-Output(MISO) configuration and Single-Input Multiple-Output (SIMO)configuration. In some embodiments, the Antenna 150 may enable a massiveMIMO configuration with tens or hundreds of antenna elements. TheAntenna 1510 may enable other multi-antenna techniques such asbeamforming. In some examples and depending on the UE 1500 capabilitiesor the type of UE 1500 (e.g., a low-complexity UE), the UE 1500 maysupport a single antenna only.

The transceiver 1520 may communicate bi-directionally, via the Antenna1510, wireless links as described herein. For example, the transceiver1520 may represent a wireless transceiver at the UE and may communicatebi-directionally with the wireless transceiver at the base station orvice versa. The transceiver 1520 may include a modem to modulate thepackets and provide the modulated packets to the Antennas 1510 fortransmission, and to demodulate packets received from the Antennas 1510.

The memory 1530 may include RAM and ROM. The memory 1530 may storecomputer-readable, computer-executable code 1535 including instructionsthat, when executed, cause the processor to perform various functionsdescribed herein. In some examples, the memory 1530 may contain, amongother things, a Basic Input/output System (BIOS) which may control basichardware or software operation such as the interaction with peripheralcomponents or devices.

The processor 1540 may include a hardware device with processingcapability (e.g., a general purpose processor, a DSP, a CPU, amicrocontroller, an ASIC, an FPGA, a programmable logic device, adiscrete gate or transistor logic component, a discrete hardwarecomponent, or any combination thereof). In some examples, the processor1540 may be configured to operate a memory using a memory controller. Inother examples, a memory controller may be integrated into the processor1540. The processor 1540 may be configured to execute computer-readableinstructions stored in a memory (e.g., the memory 1530) to cause the UE1500 or the base station 1505 to perform various functions.

The Central Processing Unit (CPU) 1550 may perform basic arithmetic,logic, controlling, and Input/output (I/O) operations specified by thecomputer instructions in the Memory 1530. The user equipment 1500 and/orthe base station 1505 may include additional peripheral components suchas a graphics processing unit (GPU) 1560 and a Global Positioning System(GPS) 1570. The GPU 1560 is a specialized circuitry for rapidmanipulation and altering of the Memory 1530 for accelerating theprocessing performance of the user equipment 1500 and/or the basestation 1505. The GPS 1570 may be used for enabling location-basedservices or other services for example based on geographical position ofthe user equipment 1500.

In some example, MBS services may be enabled via single-celltransmission. MBS may be transmitted in the coverage of a single cell.One or more Multicast/Broadcast control channels (e.g., MCCHs) and oneor more Multicast/Broadcast data channels (e.g., MTCHs) may be mapped onDL-SCH. The scheduling may be done by the gNB. The Multicast/Broadcastcontrol channel and the Multicast/Broadcast data channel transmissionsmay be indicated by a logical channel specific RNTI on PDCCH. In someexamples, a one-to-one mapping between a service identifier such as atemporary mobile group identifier (TMGI) and a RAN level identifier suchas a group identifier (G-RNTI) may be used for the reception of theDL-SCH to which a Multicast/Broadcast data channel may be mapped. Insome examples, a single transmission may be used for DL-SCH associatedwith the Multicast/Broadcast control channel and/or theMulticast/Broadcast data channel transmissions and HARQ or RLCretransmissions may not be used and/or an RLC Unacknowledged Mode (RLCUM) may be used. In other examples some feedback (e.g., HARQ feedback orRLC feedback) may be used for transmissions via Multicast/Broadcastcontrol channel and/or Multicast/Broadcast data channels.

In some example, for Multicast/Broadcast data channel, the followingscheduling information may be provided on Multicast/Broadcast controlchannel: a Multicast/Broadcast data channel scheduling cycle, aMulticast/Broadcast data channel on-duration (e.g., duration that the UEwaits for, after waking up from DRX, to receive PDCCHs), aMulticast/Broadcast data channel inactivity timer (e.g., duration thatthe UE waits to successfully decode a PDCCH, from the last successfuldecoding of a PDCCH indicating the DL-SCH to which thisMulticast/Broadcast data channel is mapped, failing which it re-entersDRX).

In some examples, one or more UE identities may be related to MBStransmissions. The one or more identities may comprise at least one of:one or more first RNTIs that identify transmissions of theMulticast/Broadcast control channel; one or more second RNTIs thatidentify transmissions of a Multicast/Broadcast data channels. The oneor more first RNTIs that identify transmissions of theMulticast/Broadcast control channel may comprise a single cell RNTI(SC-RNTI, other names may be used). The one or more second RNTIs thatidentify transmissions of a Multicast/Broadcast data channels maycomprise a G-RNTI (nG-RNTI or other names may be used).

In some examples, one or more logical channels may be related to MBStransmissions. The one or more logical channels may comprise aMulticast/Broadcast control channel. The Multicast/Broadcast controlchannel may be a point-to-multipoint downlink channel used fortransmitting MBS control information from the network to the UE, for oneor several Multicast/Broadcast data channel. This channel may be used byUEs that receive or are interested to receive MBS. The one or morelogical channels may comprise a Multicast/Broadcast data channel. Thischannel may be a point-to-multipoint downlink channel for transmittingMBS traffic data from the network.

In some examples, a procedure may be used by the UE to inform RAN thatthe UE is receiving or is interested to receive MBS service(s) via anMBS radio bearer, and if so, to inform the 5G RAN about the priority ofMBS versus unicast reception or MBS service(s) reception in receive onlymode. An example is shown in FIG. 16 . The UE may transmit a message(e.g., an MBS interest indication message) message to inform RAN thatthe UE is receiving/interested to receive or no longerreceiving/interested to receive MBS service(s). The UE may transmit themessage based on receiving one or more messages (e.g., a SIB message ora unicast RRC message) from the network for example indicating one ormore MBS Service Area Identifiers of the current and/or neighboringcarrier frequencies.

In some examples, the UE may consider an MBS service to be part of theMBS services of interest if the UE is capable of receiving MBS services(e.g., via a single cell point to multipoint mechanism); and/or the UEis receiving or interested to receive this service via a bearerassociated with MBS services; and/or one session of this service isongoing or about to start; and/or at least one of the one or more MBSservice identifiers indicated by network is of interest to the UE.

In some examples, control information for reception of MBS services maybe provided on a specific logical channel: (e.g., a MCCH). The MCCH maycarry one or more configuration messages which indicate the MBS sessionsthat are ongoing as well as the (corresponding) information on when eachsession may be scheduled, e.g., scheduling period, scheduling window andstart offset. The one or more configuration messages may provideinformation about the neighbor cells transmitting the MBS sessions whichmay be ongoing on the current cell. In some examples, the UE may receivea single MBS service at a time, or more than one MBS services inparallel.

In some example, the MCCH information (e.g., the information transmittedin messages sent over the MCCH) may be transmitted periodically, using aconfigurable repetition period. The MCCH transmissions (and theassociated radio resources and MCS) may be indicated on PDCCH.

In some examples, change of MCCH information may occur at specific radioframes/subframes/slots and/or a modification period may be used. Forexample, within a modification period, the same MCCH information may betransmitted a number of times, as defined by its scheduling (which isbased on a repetition period). The modification period boundaries may bedefined by SFN values for which SFN mod m=0, where m is the number ofradio frames comprising the modification period. The modification periodmay be configured by a SIB or by RRC signaling.

In some examples, when the network changes (some of) the MCCHinformation, it may notify the UEs about the change in the firstsubframe/slot which may be used for MCCH transmission in a repetitionperiod. Upon receiving a change notification, a UE interested to receiveMBS services may acquire the new MCCH information starting from the samesubframe/slot. The UE may apply the previously acquired MCCH informationuntil the UE acquires the new MCCH information.

In an example, a system information block (SIB) may contain theinformation required to acquire the control information associatedtransmission of MBS. The information may comprise at least one of: oneor more discontinuous reception (DRX) parameters for monitoring forscheduling information of the control information associatedtransmission of MBS, scheduling periodicity and offset for schedulinginformation of the control information associated transmission of MBS,modification period for modification of content of the controlinformation associated transmission of MBS, repetition information forrepetition of the control information associated transmission of MBS,etc.

In an example, an information element (IE) may provide configurationparameters indicating, for example, the list of ongoing MBS sessionstransmitted via one or more bearers for each MBS session, one or moreassociated RNTIs (e.g., G-RNTI, other names may be used) and schedulinginformation. The configuration parameters may comprise at least one of:one or more timer values for discontinuous reception (DRX) (e.g., aninactivity timer or an On Duration timer), an RNTI for scrambling thescheduling and transmission of a Multicast/Broadcast traffic channel(e.g., MTCH, other names may be used), ongoing MBS session, one or morepower control parameters, one or more scheduling periodicity and/oroffset values for one or more MBS traffic channels, information aboutlist of neighbor cells, etc.

In some examples a gNB or ng-eNB may comprise logical nodes that hostsome, all or parts of the user plane and/or control planefunctionalities. For example, a gNB Central Unit (gNB-CU) may be alogical node hosting RRC, SDAP and PDCP protocols of the gNB or RRC andPDCP protocols of the en-gNB that controls the operation of one or moregNB-DUs. The gNB-CU may terminate the F1 interface connected with thegNB-DU. A gNB Distributed Unit (gNB-DU) may be a logical node hostingRLC, MAC and PHY layers of the gNB or en-gNB, and its operation may bepartly controlled by gNB-CU. One gNB-DU may support one or multiplecells. One cell may be supported by only one gNB-DU. The gNB-DU mayterminate the F1 interface connected with the gNB-CU. A gNB-CU-ControlPlane (gNB-CU-CP) may be a logical node hosting the RRC and the controlplane part of the PDCP protocol of the gNB-CU for an en-gNB or a gNB.The gNB-CU-CP may terminate the E1 interface connected with thegNB-CU-UP and the F1-C interface connected with the gNB-DU. AgNB-CU-User Plane (gNB-CU-UP) may be a logical node hosting the userplane part of the PDCP protocol of the gNB-CU for an en-gNB, and theuser plane part of the PDCP protocol and the SDAP protocol of the gNB-CUfor a gNB. The gNB-CU-UP may terminate the E1 interface connected withthe gNB-CU-CP and the F1-U interface connected with the gNB-DU.

In some examples, duplication may be configured for a radio bearer byRRC, at least one secondary RLC entity is added to the radio bearer tohandle the duplicated PDCP PDUs as shown in FIG. 17 , where the logicalchannel corresponding to the first RLC entity may be referred to as theprimary logical channel, and the logical channel corresponding to thesecondary RLC entity(ies), the secondary logical channel(s). In someexamples, all RLC entities may have the same RLC mode. Duplication atPDCP may comprise submitting the same PDCP PDUs multiple times: once toeach activated RLC entity for the radio bearer. In some examples, PDCPpacket duplication may be used to enhance reliability. With multipleindependent transmission paths, packet duplication may increasereliability and reduces latency.

In some examples, when configuring duplication for a radio bearer (e.g.,DRB, multicast radio bearer (MRB), etc.), RRC may set the state of PDCPduplication (either activated or deactivated) at the time of(re-)configuration. After the configuration, the PDCP duplication statemay be dynamically controlled by means of a MAC control element and indual connectivity (DC), the UE may apply the MAC CE commands regardlessof their origin (e.g., master cell group (MCG) or secondary cell group(SCG)). In some examples, when duplication is configured for an SRB, thestate may be active and may not be dynamically controlled. In someexamples, when configuring duplication for a radio bearer (e.g., DRB,MRB, etc.) with more than one secondary RLC entity, RRC also may set thestate of each of them (e.g., either activated or deactivated).Subsequently, a MAC CE may be used to dynamically control whether eachof the configured secondary RLC entities for a DRB may be activated ordeactivated, e.g., which of the RLC entities may be used for duplicatetransmission. Primary RLC entity may not be deactivated. In someexamples, when duplication is deactivated for a radio bearer (e.g., DRB,MRB, etc.), all secondary RLC entities associated to this DRB may bedeactivated. In some examples, when a secondary RLC entity isdeactivated, it is not re-established, the HARQ buffers may not beflushed, and the transmitting PDCP entity may indicate to the secondaryRLC entity to discard duplicated PDCP PDUs.

In some examples, when activating duplication for a radio bearer (e.g.,DRB, MRB, etc.), RAN may ensure that at least one serving cell isactivated for each logical channel of the radio bearer; and when thedeactivation of SCells leaves no serving cells activated for a logicalchannel of the DRB, the RAN may ensure that duplication is alsodeactivated.

In some examples, when duplication is activated, the original PDCP PDUand the corresponding duplicate(s) may not be transmitted on the samecarrier. The primary and secondary logical channels may either belong tothe same MAC entity (e.g., referred to as CA duplication) or todifferent ones (e.g., referred to as DC or DC+CA duplication). CAduplication may be configured together with DC duplication whenduplication over more than two legs is configured in the UE. In CAduplication, logical channel mapping restrictions may be used in MAC toensure that the primary and secondary logical channels are not sent onthe same carrier. In some examples, when CA duplication is configuredfor an SRB, one of the logical channels associated to the SRB may bemapped to SpCell.

In some examples, when CA duplication is deactivated for a radio bearer(e.g., DRB, MRB, etc.), the logical channel mapping restrictions of theprimary and secondary logical channels may be lifted for as long asduplication remains deactivated.

In some examples, when an RLC entity acknowledges the transmission of aPDCP PDU, the PDCP entity may indicate to the other RLC entity(ies) todiscard it. In addition, in case of CA duplication, when an RLC entityrestricted to only SCell(s) reaches the maximum number ofretransmissions for a PDCP PDU, the UE may inform the gNB and may nottrigger radio link failure (RLF).

In some examples, if one or more radio bearers (e.g., DRBs, MRB(s),etc.) are configured with PDCP duplication, the network may activate anddeactivate the PDCP duplication for all or a subset of associated RLCentities for the configured bearer(s).

In some examples, the PDCP duplication for the configured bearer(s)(e.g., DRB(s). MRB(s), etc.) may be activated and deactivated by:receiving the Duplication Activation/Deactivation MAC CE; receiving theDuplication RLC Activation/Deactivation MAC CE; or indication by RRC.

In some examples, the PDCP duplication for all or a subset of associatedRLC entities for the configured bearer(s) (e.g., DRB(s), MRB(s), etc.)may be activated and deactivated by: receiving the Duplication RLCActivation/Deactivation MAC CE; or indication by RRC.

In some examples, if a Duplication Activation/Deactivation MAC CE isreceived activating the PDCP duplication of a radio bearer (e.g., DRB,MRB, etc.): the MAC entity may, for each radio bearer configured withPDCP duplication, indicate the activation of PDCP duplication of the DRBto upper layers.

In some examples, if a Duplication Activation/Deactivation MAC CE isreceived deactivating the PDCP duplication of the radio bearer: the MACentity may, for each radio bearer configured with PDCP duplication,indicate the deactivation of PDCP duplication of the DRB to upperlayers.

In some examples, if a Duplication RLC Activation/Deactivation MAC CE isreceived activating PDCP duplication for associated RLC entities of aradio bearer (e.g. DRB, MRB, etc.) configured with PDCP duplication: theMAC entity may, for each radio bearer configured with PDCP duplication,indicate the activation of PDCP duplication for the indicated secondaryRLC entity(ies) of the radio bearer to upper layers.

In some examples, if a Duplication RLC Activation/Deactivation MAC CE isreceived deactivating PDCP duplication for associated RLC entities of aradio bearer configured with PDCP duplication: the MAC entity may, foreach radio bearer configured with PDCP duplication, indicate thedeactivation of PDCP duplication for the indicated secondary RLCentity(ies) of the DRB to upper layers.

In some examples as shown in FIG. 18 , the DuplicationActivation/Deactivation MAC CE of one octet may be used and may beidentified by a MAC subheader with a corresponding logical channelidentifier (LCID). The MAC CE may have a fixed size and may comprise ofa single octet containing eight D-fields. The Di field may indicate theactivation/deactivation status of the PDCP duplication of radio bearer i(e.g., DRB i or MRB i) where i may be the ascending order of the DRB IDamong the DRBs configured with PDCP duplication and with RLC entity(ies)associated with this MAC entity. The Di field may be set to 1 toindicate that the PDCP duplication of DRB i may be activated. The Difield may be set to 0 to indicate that the PDCP duplication of DRB i maybe deactivated.

In some examples, the Duplication RLC Activation/Deactivation MAC CE maybe identified by a MAC subheader with a corresponding logical channelidentifier. The MAC CE mah have a fixed size and may comprise of asingle octet as shown in FIG. 19 . The bearer ID field may indicates theidentity of bearer (e.g., DRB, MRB, etc.) for which the MAC CE applies.The RLCi field may indicate the activation/deactivation status of PDCPduplication for the RLC entity i where i may be ascending order oflogical channel ID of secondary RLC entities in the order of MCG andSCG, for the radio bearer. The RLCi field may be set to 1 to indicatethat the PDCP duplication for the RLC entity i may be activated. TheRLCi field may be set to 0 to indicate that the PDCP duplication for theRLC entity i may be deactivated.

The PDCP sequence number (SN) may have a length of 12, or 18 bits Thelength of the PDCP SN may be configured by upper layers (e.g., via apdcp-SN-SizeUL, pdcp-SN-SizeDL, or sl-PDCP-SN-Size information element).

In an example, a COUNT parameter may have a length of 32 bits may thecount value may be composed of a HFN and the PDCP SN. The size of theHFN part in bits may be equal to 32 minus the length of the PDCP SN.

In some examples, when upper layers request a PDCP entityre-establishment, for acknowledged mode (AM) radio bearers (e.g., DRBs,MRBs, etc.) which were not suspended, from the first PDCP SDU for whichthe successful delivery of the corresponding PDCP Data PDU has not beenconfirmed by lower layers, a transmitting PDCP entity may performretransmission or transmission of all the PDCP SDUs already associatedwith PDCP SNs in ascending order of the COUNT values associated to thePDCP SDU prior to the PDCP entity re-establishment. The transmittingPDCP entity may perform header compression of the PDCP SDU using ROHC,perform integrity protection and ciphering of the PDCP SDU using theCOUNT value associated with this PDCP SDU and submit the resulting PDCPData PDU to lower layer.

In some examples, For AM DRBs, when upper layers request a PDCP datarecovery for a radio bearer, the transmitting PDCP entity may: performretransmission of all the PDCP Data PDUs previously submitted tore-established or released AM RLC entities in ascending order of theassociated COUNT values for which the successful delivery has not beenconfirmed by lower layers.

In some examples, for radio bearers (e.g., for DAPS bearers), when upperlayers request uplink data switching, for AM DRBs, from the first PDCPSDU for which the successful delivery of the corresponding PDCP Data PDUhas not been confirmed by the RLC entity associated with the sourcecell, the transmitting PDCP entity may perform retransmission ortransmission of all the PDCP SDUs already associated with PDCP SNs inascending order of the COUNT values associated to the PDCP SDU prior touplink data switching to the RLC entity associated with the target cell.The transmitting PDCP entity may perform header compression of the PDCPSDU using ROHC; perform integrity protection and ciphering of the PDCPSDU using the COUNT value associated with this PDCP SDU; submit theresulting PDCP Data PDU to lower layer.

In some examples, network controlled mobility may apply to UEs inRRC_CONNECTED and may be categorized into two types of mobility: celllevel mobility and beam level mobility. The cell Level Mobility mayrequire explicit RRC signaling to be triggered, i.e. handover. Forinter-gNB handover, the signaling procedures consist of at least thefollowing elemental components as shown in FIG. 20 : The source gNB mayinitiate handover and issues a HANDOVER REQUEST over the Xn interface.The target gNB may perform admission control and provides the new RRCconfiguration as part of the HANDOVER REQUEST ACKNOWLEDGE. The sourcegNB may provide the RRC configuration to the UE by forwarding theRRCReconfiguration message received in the HANDOVER REQUEST ACKNOWLEDGE.The RRCReconfiguration message may include at least cell ID andinformation required to access the target cell so that the UE may accessthe target cell without reading system information. For some cases, theinformation required for contention-based and contention-free randomaccess may be included in the RRCReconfiguration message. The accessinformation to the target cell may include beam specific information, ifany. The UE may move the RRC connection to the target gNB and may replywith the RRCReconfigurationComplete.

In some examples, in case of dual active protocol stack (DAPS) handover,the UE may continue the downlink user data reception from the source gNBuntil releasing the source cell and may continue the uplink user datatransmission to the source gNB until successful random access procedureto the target gNB.

In some examples, the handover mechanism triggered by RRC may requirethe UE at least to reset the MAC entity and re-establish RLC, except forDAPS, where upon reception of the handover command, the UE may: create aMAC entity for target; establishes the RLC entity and an associated DTCHlogical channel for target for each DRB configured with DAPS; for theDRB configured with DAPS, reconfigure the PDCP entity with separatesecurity and ROHC functions for source and target and may associate themwith the RLC entities configured by source and target respectively; andretain the rest of the source configurations until release of thesource.

In some examples, RRC managed handovers with and without PDCP entityre-establishment may both be supported. For radio bearers (e.g., DRBs,MRBs, etc.) using RLC AM mode, PDCP may either be re-establishedtogether with a security key change or may initiate a data recoveryprocedure without a key change. In some examples, for DRBs or MRBs usingRLC UM mode and for SRBs, PDCP may either be re-established togetherwith a security key change or may remain as it is without a key change.

In some examples, Beam Level Mobility may not require explicit RRCsignaling to be triggered. The gNB may provide, via RRC signaling, theUE with measurement configuration containing configurations of SSB/CSIresources and resource sets, may report and trigger states fortriggering channel and interference measurements and reports. Beam LevelMobility may be dealt with at lower layers by means of physical layerand MAC layer control signaling, and RRC may not be required to knowwhich beam is being used at a given point in time.

In some examples, for RLC-AM bearers: for in-sequence delivery andduplication avoidance, PDCP SN may be maintained on a per radio bearer(e.g., DRB, MRB) basis and the source gNB may inform the target gNBabout the next DL PDCP SN to allocate to a packet which may not have aPDCP sequence number yet (either from source gNB or from the UPF). Inboth the UE and the target gNB, a window-based mechanism may be used forduplication detection and reordering. The occurrence of duplicates overthe air interface in the target gNB may be minimized by means of PDCP SNbased reporting at the target gNB by the UE. In uplink, the reportingmay be optionally configured on a per radio bearer (DRB, MRB, etc.)basis by the gNB and the UE may first start by transmitting thosereports when granted resources are in the target gNB. The target gNB mayre-transmit and prioritizes downlink data forwarded by the source gNB(e.g., the target gNB may first send forwarded PDCP SDUs with PDCP SNs,then forwarded downlink PDCP SDUs without SNs before sending new datafrom 5GC), excluding PDCP SDUs for which the reception was acknowledgedthrough PDCP SN based reporting by the UE. In some example, the UE mayre-transmit in the target gNB all uplink PDCP SDUs starting from theoldest PDCP SDU that has not been acknowledged at RLC in the source,excluding PDCP SDUs for which the reception was acknowledged throughPDCP SN based reporting by the target.

In some examples, an IE PDCP-Config may be used to set the configurablePDCP parameters for signaling and data radio bearers.

In some examples, the IE RLC-BearerConfig may be used to configure anRLC entity, a corresponding logical channel in MAC and the linking to aPDCP entity (served radio bearer). A parameter logicalChannelIdentitymay indicate ID used commonly for the MAC logical channel and for theRLC bearer. A parameter reestablishRLC may indicate that RLC may bere-established. Network may set this to true at least whenever thesecurity key used for the radio bearer associated with this RLC entitychanges. For SRB2 and DRBs, it may be set to true during the resumptionof the RRC connection or the first reconfiguration afterreestablishment. A parameter rlc-Config may indicate the RLC mode (UM,AM) and may provide corresponding parameters. RLC mode reconfigurationmay be performed by radio bearer (e.g., DRB) release/addition or fullconfiguration. A parameter servedRadioBearermay associate the RLC bearerwith an SRB, a DRB or an MRB. The UE may deliver DL RLC SDUs receivedvia the RLC entity of this RLC bearer to the PDCP entity of theservedRadioBearer. The UE may advertise and deliver uplink PDCP PDUs ofthe uplink PDCP entity of the servedRadioBearer to the uplink RLC entityof this RLC bearer unless the uplink scheduling restrictions(moreThanOneRLC in PDCP-Config and the restrictions inLogicalChannelConfig) forbid it to do so.

In an example, the IE RLC-Config may be used to specify the RLCconfiguration of SRBs and DRBs.

In some examples, a UE and/or network may use mechanisms to enablemulticast and broadcast transmission of data within a cell and acrossmultiple cells assuming no reliance on large area single frequencynetworks (SFN). In some examples, the mechanisms may be based on SingleCell point to multipoint (PTM) framework. Example embodiments enableconfiguration of multicast/broadcast bearers and their servicecontinuities and reliable deliveries by enhancements to the packet dataconvergence protocol (PDCP) sub-layer of layer 2.

In existing solutions for multicast broadcast services (MBS), the MBSdata may be transmitted without layer 2 encryption and headercompression and the PDCP packet retransmission or forwarding may not beused. In some examples, due to diversity of traffic types, applicationsand use cases, the encryption and/or header compression may be used. Insome examples, the packet duplication and retransmission of missingpackets, which may be part of PDCP function, may be used for MBStransmissions. At least some of the PDCP functions may be used for MBS.Existing PDCP solutions may not consider CU-DU architecture and packetduplication operation in PDCP design. Example embodiments enhance thePDCP functionalities in connection with the MBS services.

In some examples, the configuration of PDCP for multicast and broadcastservices may take into account the possibility of no feedback ormultiple feedback channels for the same PDCP transmission. In someexamples, a single PDCP instantiation for MBS may be configured andassociated with multiple RLC channels toward a distributed unit (DU) ora UE within a DU. In some examples, the packet duplication functionalityof PDCP may be used differently in MBS and unicast radio bearers (e.g.,MRBs and DRBs, respectively). In some examples, different set of PDCPfunctions for different MBS services (e.g., corresponding to differentMulticast Radio Bearers (MRBs)) may be supported/configured. Forexample, different MBS services may have different requirements (e.g.,different services continuity requirements). The use of PDCP functionsand their configuration for MRBs may be different from those used forDRB and may also be different across different MRBs.

In some examples, from PDCP perspective, a common set of parameters suchas Sequence Number, encryption, header compression may be applied forall MBS data for a given MRB. In some examples, to avoid too manysimilar PDCP configurations, a common PDCP may be configured and usedfor each MRB. A common PDCP may be configured for UEs receiving MBS forthe same MRB.

In some examples, the same common MBS PDCP entity may be reused forunicast transmission when changing from multicast to unicast fordelivering an MBS service. In an example, or a new PDCP entity may beconfigured when changing from multicast to unicast for delivering an MBSservice. In some examples, the higher layer attributes of MBR may bemaintained regardless of unicast or multicast delivery at lower layersand the same PDCP instance may be reused when transmission is switchedfrom multicast to unicast. In some examples, when MBS transmission fromgNB is switched from multicast to unicast, the same PDCP instance andconfiguration may be reused.

In some examples, the MBS data may be transmitted from multiple nodeswithin a RAN, for example from multiple DUs within a gNB or multipleremote unites (RUs)/transmission reception points (TRPs). In someexamples, while the configuration of MRB and its higher layer attributesmay be configured at the CU both in terms of user plane and controlplane, the mode of MBS transmission control, e.g., multicast vs unicast,and timing of scheduling may be controlled by the MAC at each DU. Insome examples, higher layer attributes and configurations of MRB at userand control plane may be set by CU while flexible scheduling of MBS datamay be managed by MAC within a DU.

In some examples, when MBS is offered through multiple DUs, the RANdelivery across each DU may be observed and managed by the CU. A commonPDCP may be configured per MRB and the PDCP within CU of a gNB mayduplicate PDCP service data units (SDUs) associated with a MBS serviceflow to all DUs. In some examples, one RLC entity may be defined/trackedfor each DU used for MBS transmission. The PDCP entity may duplicatePDCP SDU across all RLC entities associated with DU transmitted MBSdata. In some examples, one PDCP instance may be configured for each DUand associated RLC entity.

In some examples, a common PDCP may be configured for transmission ofmulticast data associated with an MRB. In this case, the PDCP SDUs maybe duplicated across all DUs and a unique RLC entity may be configuredand tracked for SDU deliveries, for MBS transmission associated witheach MRB on each DU.

In some examples, for each DU involved in MBS, a separate PDCP instanceand RLC entity may be configured in the CU for each MRB.

In some examples, to improve reliability, a UE may be configured withmulti-connectivity for reception of MBS at the beam, the remote unit(RU) or at the DU level. In some examples, to enable themulti-connectivity at the DU level, a UE may be configured with PDCPpacket duplication.

In some examples, the PDCP packet duplication for the configured MRB(s)may be activated and deactivated by for all or a subset of associatedRLC entities by receiving the PDCP packet duplication RLCActivation/Deactivation MAC CE or based on indication by RRC.

In some examples, a UE may be configured for multi-connectivity, atbeam/RU or DU level, for reliable MBS reception. In some example, forMRB reception, the UE may be configured with PDCP duplication.

The concepts of Common PDCP, PDCP duplication and multi-connectivitywith a common PDCP for all UEs in one DU and a common PDCP withduplication across DUs are shown in FIG. 21A and FIG. 21B.

In some examples, to enable in-sequence delivery by PDCP, a singlesequence number may be maintained at the PDCP entity and the RLC mayhandle any retransmission. In some examples, one Sequence Number foreach DU may be maintained so if retransmission at PDCP is needed it canbe handled selectively for each DU. In some examples, the PDCP entitymay maintain and track one SN for MBS data associated with an MRB forall DUs or may have separate SN for each DU.

In some examples, the PDCP may enable in-sequence delivery of MBSpackets in dual connectivity cases or mobility between cells. In someexamples, a UE may be in connected state in source cell and may start anew connection as part of HO with a target cell using Dual ActiveProtocol Stack (DAPS). The UE in connected state may maintain receptionof MBS from source cell using the common PDCP while establishing a newconnection with a target cell for unicast services. In some examples, aUE may be in connected state in both cells: this may be a dualconnectivity scenarios where MBR may be delivered only from one cell,e.g. Cell 1, while some or all DRBs may be delivered by the other cell.In some examples, a UE may be connected with unicast cell, e.g. Cell 2for unicast data, but may receive MBS from the Cell 1 without having anRRC connection to Cell 1. Example use of common PDCP for MBS receptionby UEs in DC, DAP and Idle/Inactive States is shown in FIG. 22 . In allcases, a UE may receive PDCP SDUs from the common PDCP andretransmission and if any unicast transmission is needed, they may beforwarded to cell 2. The common PDCP of a source MBS cell may be used todeliver MBS data to UEs in handover with DAPS and dual connectivity witha target cell or to idle/connected UEs which may be connected forunicast in nearby cells.

In some examples, header compression may be used for MBS services suchas VoIP application for missional critical group calls and support forshort packet transmissions in IIoT applications. In some examples, tosupport such use cases, header compressions may be used for IP andEthernet packets. A variation of robust header compression (ROHC) may beused for IP traffic and the Ethernet header compression may be used forIIoT multicast traffic. In either case options may be considered withdownlink only signaling if no feedback and uplink is used for MBS, e.g.in broadcast only mode.

In some examples, the ROHC scheme may have three modes of operation:Unidirectional, Bidirectional Optimistic, and Bidirectional Reliablemode. Which mode would be the best one in a certain situation may dependon the characteristics of the environment of the compression protocol,such as feedback abilities, error probabilities and distributions,effects of header size variation, etc. In some examples, headercompression schemes without uplink feedback, such as Unidirectional modeof ROHC, may be used for those MBRs which do not require feedbackchannels.

In some examples, L2 encryption may be used for MBS data and suchcapability may be needed in some of MBS use cases in 5G. In someexamples, a common encryption at PDCP layer may be used which may beconfigurable based on whether traffic is multicast with feedback orbroadcast without feedback. The UEs may be given the Keyes at the timeof registration with MBS service and key updates may be provided to UEsusing unicast or multicast transmission. The UEs may move to connectedstate to support signaling needed for key updates. In some examples,Layer 2 encryption for MBS may be used at PDCP and key exchange andupdate signaling may be supported through unicast or multicast RRCsignaling for UEs in connected state.

In an example embodiment as shown in FIG. 23 , a UE may receive one ormore messages (e.g., one or more RRC messages) comprising configurationparameters of one or more cells. The configuration parameters maycomprise first configuration parameter of a multicast radio bearer (MRB,also referred to as MBS radio bearer in this disclosure) associated witha first MBS service. The configuration parameters of the MRB maycomprise one or more of an MRB identifier, parameters associated withthe quality of service (QoS) requirements of the MRB, securityparameters, PDCP configuration parameters associated with the MRB, etc.The UE may receive the configuration parameters from a base station(gNB) that comprises a central unit (CU) and a plurality of distributedunits (DUs) comprising a first DU and a second DU. Some of the protocolterminations (e.g., PDCP) of the base station may reside in the CU andsome of the protocol terminations may reside in the DUs (e.g., RLC, MAC,PHY). A PDCP entity may be established for the MRB at the CU of the gNB.In an example, the PDCP entity may be commonly established for the firstDU and the second DU. The PDCP entity may be commonly established for afirst RLC entity of the first DU and a second RLC entity of the secondDU. The PDCP entity at the CU may utilize a PDCP duplication process togenerate a PDCP PDU and a duplicate of the PDCP PDU. The PDCP entity mayforward the PDCP PDU associated with the MRB to the first DU and theduplicate of the PDCP PDU to the second DU. The forwarding of the PDCPPDUs to the DUs may be based on F1 interfaces between the CU and theDUs. The first DU may receive the PDCP PDU via a first F1 interface andthe second DU may receive the PDCP PDU via a second F1 interface. ThePDCP PDU may be processed by the RLC and MAC/PHY established in thefirst DU (e.g., a first RLC and a first MAC/PHY) and the UE may receivea first transport block that comprises the PDCP PDU. In an example, theduplicate of the PDCP DU may be processed by the RLC and MAC/PHYestablished in the second DU (e.g., a second RLC and a second MAC/PHY).The second DU may transmit the duplicate of the PDCP PDU. In an example,the second DU may transmit a second transport block comprising theduplicate of the PDCP PDU. In an example, the second DU may transmit thesecond transport block to the UE. The UE may decode the first transportblock and the second transport block to enhance the reliability ofreception of the first MBS service data by transmitting both the PDCPPDU and a duplicate of the PDCP PDU to the UE. In some examples, the UEmay receive a PDCP packet duplication activation signaling indicatingactivation of the packet duplication for the MRB at the UE.

In an example embodiment as shown in FIG. 24 , a base station maycomprise a central unit (CU), a first distributed unit (DU) and a seconddistributed unit (DU). The base station may establish, at the CU, atleast one PDCP entity for an MRB associated with a first MBS service. Insome examples, the at least one PDCP entity mat be established for boththe MRB and a unicast radio bearer (e.g., a DRB) that are associatedwith the first MBS service and the base station may switch between theMRB and the DRB or use both MRB and DRB for delivering the first MBSservice to the UEs. In some examples, the MRB (or the MRB and the DRB)may be acknowledged mode (AM) radio bearers and/or may be associatedwith RLC entities that use AM RLC functionalities. The at least one PDCPentity may utilize a PDCP packet duplication process to generate a PDCPPDU and a duplicate of the PDCP PDU. The PDCP PDU (and the duplicatePDCP PDU) may be generated based on an incoming IP packet of the firstMBS service flow associated with the MRB (or the MRB and the DRB in casethe at least one PDCP entity may be associated with both an MBS bearerand a unicast bearer). The PDCP PDU and the duplicate PDCP PDU may beforwarded (e.g., using F1 interfaces) to the first DU and the second DUrespectively. In examples, the gNB may establish a first RLC entity atthe first DU for processing the PDCP packet and a second RLC entity atthe second DU for processing the duplicate PDCP packet. In some example,the at last one PDCP entity may be a single PDCP entity commonlyestablished for the first RLC entity and the second RLC entity. In someexamples, the at least one PDCP entity may comprise a first PDCP entityfor the first RLC entity and a second PDCP entity for the second RLCentity. In some examples, the gNB may establish a first MAC entityassociated with the first RLC entity at the first DU and a second MACentity associated with the second RLC entity at the second DU. The firstMAC entity may perform scheduling functions for one or more first UEsserved by the first DU and the second MAC entity may perform schedulingfunctions for one or more second UEs served by the second DU.

The PDCP entity may maintain separate PDCP sequence numbers for the PDCPPDU and the duplicate of the PDCP PDU (e.g., a first PDCP SN for thePDCP PDU and a second PDCP SN for the duplicate of the PDCP PDU). ThePDCP PDU may be processed by the RLC and MAC/PHY at the first DU and maybe transmitted via the first DU and the duplicate PDCP PDU may beprocessed by the RLC and MAC/PHY at the second DU and may be transmittedvia the second DU.

The PDCP entity may be triggered to retransmit PDCP packets. Forexample, the trigger for PDCP packet retransmission may be based on aPDCP packet re-establishment process. For example, the trigger for PDCPpacket retransmission may be based on a handover procedure (e.g., a DAPShandover, etc.). For example, the trigger for PDCP packet retransmissionmay be in response to uplink data switching during a handover procedure(e.g., DAPS). In some examples, the handover procedure may use asequence number (SN) status transfer procedure to transmit an SN statustransfer message to a target base station. The SN status transfermessage may comprise the first PDCP SN associated with the PDCP packetand the second PDCP SN associated with the duplicate PDCP packet. Forexample, the trigger for PDCP packet retransmission may be in responseto an automatic repeat request (ARQ) process at the PDCP layerdetermining the retransmission of the PDCP packets. For example, thetrigger for PDCP packet retransmission may be in response to a PDCPrecovery procedure.

In response to the trigger for retransmission of the PDCP packets, thegNB may retransmit the PDCP packet based on the first PDCP SN and thesecond PDCP SN. For example, based on the firs PDCP SN and the secondPDCP SN, the gNB may selectively retransmit the PDP packet via the firstDU or the duplicate PDCP packet via the second DU. For example, the basestation may retransmit at least one of: the first PDCP packet based onthe first PDCP SN and the duplicate of the PDCP packet based on thesecond SN.

In an embodiment, a user equipment (UE) may receive from a base station(BS), configuration parameters of a multicast radio bearer (MRB)associated with a first MBS service, wherein the BS comprises a centralunit (CU), a first distributed unit (DU) and a second DU. The UE mayreceive, from the first DU, a transport block associated with the MRB,wherein: the transport block may comprise a packet data convergenceprotocol (PDCP) packet; the first DU may receive the PDCP packet from aPDCP entity, established in the CU of the BS, via a first interface; thesecond DU may receive a duplicate of the PDCP packet from the PDCPentity via a second interface; and the duplicate of the PDCP packet maybe transmitted via the second DU.

In some embodiments, a first radio link control (RLC) entity may beestablished in the first distributed unit (DU) for transmission of thefirst packet data convergence protocol (PDCP) packet; and a second RLCentity may be established in the second DU for transmission of theduplicate of the PDCP packet. In some embodiments, the packet dataconvergence protocol (PDCP) entity may be commonly established for thefirst radio link control (RLC) entity and the second RLC entity.

In some embodiments, the UE may receive a second transport block,comprising the duplicate of the packet data convergence protocol (PDCP)packet, from the second distributed unit (DU). In some embodiments, theUE may decode the transport block and the second transport block forenhancing reliability of reception of the first multicast broadcastservice (MBS) service.

In some embodiments, the packet data convergence protocol (PDCP) entitymay utilize a packet duplication process to generate the duplicate ofthe PDCP packet.

In some embodiments, the UE may receive a packet data convergenceprotocol (PDCP) packet duplication activation signaling indicationactivation of PDCP packet duplication for the multicast radio bearer(MRB).

In an embodiment, a base station (BS) may establish, at a central unit(CU) of the BS, at least one packet data convergence protocol (PDCP)entity for a multicast radio bearer (MRB) associated with a first MBSservice. The base station may provide, via a PDCP entity, a first PDCPsequence number (SN) associated with a PDCP packet. The PDCP SN may befurther associated with a first distributed unit (DU) of the BS. Thebase station may provide, via the PDCP entity, a second PDCP SNassociated with a duplicate of the PDCP packet and further associatedwith a second DU of the BS. The base station may transmit at least oneof the PDCP packet and the duplicate of the PDCP packet based on thefirst PDCP SN and the second PDCP SN.

In some embodiments, the base station may also establish a first radiolink control (RLC) entity for the PDCP packet transmitted via the firstdistributed unit (DU). The base station may also establish a a secondRLC entity for the duplicate of the PDCP packet transmitted via thesecond DU. In some embodiments, the first RLC entity is established atthe first DU of the BS; and the second RLC entity is established at thesecond DU of the BS.

In some embodiments, the base station commonly establishes at least onePDCP entity for the first RLC entity and the second RLC entity. In someembodiments, the at least one PDCP entity corresponds to a first PDCPentity and a second PDCP entity. The first PDCP entity is establishedfor the first RLC entity. The second PDCP entity is established for thesecond RLC entity.

In some embodiments, the base station further establishes a first mediumaccess control (MAC) entity, associated with the first RLC entity, fortransmission of a first MAC protocol data unit (PDU) via the first DU.The base station further establishes a second MAC entity, associatedwith the second RLC entity, for transmission of a second MAC PDU via thesecond DU. Still further, in some embodiments, the base station furtherestablishes a data radio bearer (DRB) associated with the first MBSservice.

In some embodiments, in response to a trigger for PDCP packetretransmission, the base station retransmits at least one of the PDCPpacket and the duplicate of the PDCP packet based on the first PDCP SNand the second PDCP SN. In some embodiments, the trigger for the PDCPretransmission indicates a re-establishment of the PDCP entity.Additionally, in some embodiments, the trigger occurs in response tostarting a handover procedure. In other embodiments, the trigger is inresponse to a PDCP data recovery procedure.

In an embodiment, a base station (BS) may establish, at a central unit(CU) of the BS, at least one packet data convergence protocol (PDCP)entity for a multicast radio bearer (MRB) associated with a firstmulticast broadcast service (MBS) service. The PDCP entity may maintaina first PDCP sequence numbers (SN) associated with a PDCP packettransmitted via a first distributed unit (DU) of the BS; and a secondPDCP SN associated with a duplicate of the PDCP packet transmitted via asecond DU of the BS. In response to a trigger for PDCP packetretransmission, the BS may retransmit at least one of the PDCP packetand the duplicate of the PDCP packet based on the first PDCP SN and thesecond PDCP SN.

In some embodiments, the base station may establish a first radio linkcontrol (RLC) entity for the first PDCP packet transmitted via the firstdistributed unit (DU); and a second RLC entity for the duplicate of thePDCP packet transmitted via the second DU. In some embodiments, thefirst radio link control (RLC) entity may be established at the firstdistributed unit (DU) of the base station (BS); and the second RLCentity may be established at the second DU of the BS. In someembodiments, the at least one packet data convergence protocol (PDCP)entity may be a single PDCP entity commonly established for the firstradio link control (RLC) entity and the second RLC entity. In someembodiments, the at least one packet data convergence protocol (PDCP)entity may comprise a first PDCP entity, established for the first radiolink control (RLC) entity, and a second PDCP entity, established for thesecond radio link control (RLC) entity. In some embodiments, the basestation may establish: a first medium access control (MAC) entity,associated with the first radio link control (RLC) entity, fortransmission of a first MAC protocol data unit (PDUs) via the firstdistributed unit (DU); and a second MAC entity, associated with thesecond RLC entity, for transmission of a second MAC PDU via the secondDU.

In some embodiments, the at least one packet data convergence protocol(PDCP) entity may further be established for a data radio bearer (DRB)associated with the first MBS service.

In some embodiments, the at least one packet data convergence protocol(PDCP) entity may utilize a PDCP duplication process to generate theduplicate of the PDCP packet. In some embodiments, an internet protocol(IP) packet, associated with the multicast radio bearer (MRB), may beduplicated by the packet data convergence protocol (PDCP) duplicationprocess to generate the first PDCP packet and the duplicate of the PDCPpacket.

In some embodiments, the multicast radio bearer (MRB) may be anacknowledged mode (AM) radio bearer. In some embodiments, the firstradio link control (RLC) entity and the second RLC entity may beacknowledged mode (AM) RLC entities.

In some embodiments, the trigger for packet data convergence protocol(PDCP) retransmission may indicate a re-establishment of the PDCPentity.

In some embodiments, the trigger may be in response to starting ahandover procedure. In some embodiments, the handover procedure may be adual active protocol stack (DAPS) handover. In some embodiments, thehandover procedure may comprise uplink data switching.

In some embodiments, the handover procedure may comprise transmitting,by the base station (BS), a sequence number (SN) status transfer messageto a target BS; and the SN status transfer message may comprise thefirst packet data convergence protocol (PDCP) SN associated with thePDCP packet and the second PDCP SN associated with the duplicate of thePDCP packet.

In some embodiments, the trigger may be in response to a packet dataconvergence protocol (PDCP) data recovery procedure.

In some embodiments, the first packet data convergence protocol (PDCP)sequence numbers (SN) and the second PDCP SN may have a fixed lengththat is one of twelve bits or eighteen bits.

In some embodiments, the first packet data convergence protocol (PDCP)sequence number (SN) may be included in a first header of the first PDCPpacket; and the second PDCP SN may be included in a second header of thesecond PDCP packet.

In some embodiments, retransmitting the packet data convergence protocol(PDCP) packet may comprise at least one of: retransmitting the firstPDCP packet based on the first PDCP sequence number (SN); andretransmitting the duplicate of the PDCP packet based on the second PDCPSN.

The exemplary blocks and modules described in this disclosure withrespect to the various example embodiments may be implemented orperformed with a general-purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA), or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.Examples of the general-purpose processor include but are not limited toa microprocessor, any conventional processor, a controller, amicrocontroller, or a state machine. In some examples, a processor maybe implemented using a combination of devices (e.g., a combination of aDSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described in this disclosure may be implemented inhardware, software executed by a processor, firmware, or any combinationthereof. Instructions or code may be stored or transmitted on acomputer-readable medium for implementation of the functions. Otherexamples for implementation of the functions disclosed herein are alsowithin the scope of this disclosure. Implementation of the functions maybe via physically co-located or distributed elements (e.g., at variouspositions), including being distributed such that portions of functionsare implemented at different physical locations.

Computer-readable media includes but is not limited to non-transitorycomputer storage media. A non-transitory storage medium may be accessedby a general purpose or special purpose computer. Examples ofnon-transitory storage media include, but are not limited to, randomaccess memory (RAM), read-only memory (ROM), electrically erasableprogrammable ROM (EEPROM), flash memory, compact disk (CD) ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, etc. A non-transitory medium may be used to carry or storedesired program code means (e.g., instructions and/or data structures)and may be accessed by a general-purpose or special-purpose computer, ora general-purpose or special-purpose processor. In some examples, thesoftware/program code may be transmitted from a remote source (e.g., awebsite, a server, etc.) using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave. In such examples, the coaxialcable, fiber optic cable, twisted pair, DSL, or wireless technologiessuch as infrared, radio, and microwave are within the scope of thedefinition of medium. Combinations of the above examples are also withinthe scope of computer-readable media.

As used in this disclosure, use of the term “or” in a list of itemsindicates an inclusive list. The list of items may be prefaced by aphrase such as “at least one of” or “one or more of”. For example, alist of at least one of A, B, or C includes A or B or C or AB (i.e., Aand B) or AC or BC or ABC (i.e., A and B and C). Also, as used in thisdisclosure, prefacing a list of conditions with the phrase “based on”shall not be construed as “based only on” the set of conditions andrather shall be construed as “based at least in part on” the set ofconditions. For example, an outcome described as “based on condition A”may be based on both a condition A and a condition B without departingfrom the scope of this disclosure.

In this specification the terms “comprise”, “include” or “contain” maybe used interchangeably and have the same meaning and are to beconstrued as inclusive and open-ending. The terms “comprise”, “include”or “contain” may be used before a list of elements and indicate that atleast all of the listed elements within the list exist but otherelements that are not in the list may also be present. For example, if Acomprises B and C, both {B, C} and {B, C, D} are within the scope of A.

The present disclosure, in connection with the accompanied drawings,describes example configurations that are not representative of all theexamples that may be implemented or all configurations that are withinthe scope of this disclosure. The term “exemplary” should not beconstrued as “preferred” or “advantageous compared to other examples”but rather “an illustration, an instance or an example.” By reading thisdisclosure, including the description of the embodiments and thedrawings, it will be appreciated by a person of ordinary skills in theart that the technology disclosed herein may be implemented usingalternative embodiments. The person of ordinary skill in the art wouldappreciate that the embodiments, or certain features of the embodimentsdescribed herein, may be combined to arrive at yet other embodiments forpracticing the technology described in the present disclosure. Thus, thedisclosure is not limited to the examples and designs described hereinbut is to be accorded the broadest scope consistent with the principlesand novel features disclosed herein.

-   -   Clause 1. A method of multicast broadcast service (MBS) data        transmission, comprising:

establishing, by a base station (BS) at a central unit (CU) of the BS,at least one packet data convergence protocol (PDCP) entity for amulticast radio bearer (MRB) associated with a first MBS service;

providing, by the PDCP entity, a first PDCP sequence number (SN)associated with a PDCP packet and further associated with a firstdistributed unit (DU) of the BS;

providing, by the PDCP entity, a second PDCP SN associated with aduplicate of the PDCP packet and further associated with a second DU ofthe BS; and

transmitting, by the BS, at least one of the PDCP packet and theduplicate of the PDCP packet based on the first PDCP SN and the secondPDCP SN.

-   -   Clause 2. The method of Clause 1 further comprising establishing        by the BS:

a first radio link control (RLC) entity for the PDCP packet transmittedvia the first distributed unit (DU); and

a second RLC entity for the duplicate of the PDCP packet transmitted viathe second DU.

-   -   Clause 3. The method of Clause 2, wherein:

the first RLC entity is established at the first DU of the BS; and

the second RLC entity is established at the second DU of the BS.

-   -   Clause 4. The method of Clause 2, wherein the at least one PDCP        entity is a single PDCP entity commonly established for the        first RLC entity and the second RLC entity.    -   Clause 5. The method of Clause 2, wherein the at least one PDCP        entity comprises a first PDCP entity, established for the first        RLC entity, and a second PDCP entity, established for the second        RLC entity.    -   Clause 6. The method of Clause 2 further comprising        establishing:

a first medium access control (MAC) entity, associated with the firstRLC entity, for transmission of a first MAC protocol data unit (PDU) viathe first DU; and

a second MAC entity, associated with the second RLC entity, fortransmission of a second MAC PDU via the second DU.

-   -   Clause 7. The method of Clause 1 further comprising establishing        a data radio bearer (DRB) associated with the first MBS service.    -   Clause 8. The method of claim 1 further comprising in response        to a trigger for PDCP packet retransmission, retransmitting, by        the BS, at least one of the PDCP packet and the duplicate of the        PDCP packet based on the first PDCP SN and the second PDCP SN.    -   Clause 9. The method of Clause 8, wherein the trigger for the        PDCP retransmission indicates a re-establishment of the PDCP        entity.    -   Clause 10. The method of Clause 8, wherein the trigger occurs in        response to starting a handover procedure.    -   Clause 11. The method of Clause 8, wherein the trigger is in        response to a PDCP data recovery procedure.    -   Clause 12. A method of multicast broadcast service (MBS) data        transmission, comprising:

establishing, by a base station (BS) at a central unit (CU) of the BS,at least one packet data convergence protocol (PDCP) entity for amulticast radio bearer (MRB) associated with a first MBS service;

maintaining, by the PDCP entity:

a first PDCP sequence number (SN) associated with a PDCP packettransmitted via a first distributed unit (DU) of the BS; and

a second PDCP SN associated with a duplicate of the PDCP packettransmitted via a second DU of the BS; and

in response to a trigger for PDCP packet retransmission, retransmitting,by the BS, at least one of the PDCP packet and the duplicate of the PDCPpacket based on the first PDCP SN and the second PDCP SN.

-   -   Clause 13. The method of Clause 12 further comprising        establishing by the base station:

a first radio link control (RLC) entity for the PDCP packet transmittedvia the first DU; and

a second RLC entity for the duplicate of the PDCP packet transmitted viathe second DU.

-   -   Clause 14. The method of Clause 13, wherein:

the RLC entity is established at the first DU of the BS; and

the second RLC entity is established at the second DU of the BS.

-   -   Clause 15. The method of Clause 13, wherein the at least one        PDCP entity is a single PDCP entity commonly established for the        first RLC entity and the second RLC entity.    -   Clause 16. The method of Clause 13, wherein the at least one        PDCP entity comprises a first PDCP entity, established for the        first RLC entity, and a second PDCP entity, established for the        second RLC entity.    -   Clause 17. The method of Clause 13 further comprising        establishing:

a first medium access control (MAC) entity, associated with the firstradio link control (RLC) entity, for transmission of a first MACprotocol data unit (PDU) via the first distributed unit (DU); and

a second MAC entity, associated with the second RLC entity, fortransmission of a second MAC PDU via the second DU.

-   -   Clause 18. The method of Clause 12 further comprising        establishing a data radio bearer (DRB) associated with the first        MBS service.    -   Clause 19. The method of Clause 12 further comprising        generating, by the PDCP entity, the duplicate of the PDCP packet        utilizing a PDCP duplication process.    -   Clause 20. The method of Clause 19, wherein an internet protocol        (IP) packet, associated with the MRB, is duplicated by the PDCP        duplication process to generate the first PDCP packet and the        duplicate PDCP packet.    -   Clause 21. The method of Clause 12, wherein the multicast radio        bearer (MRB) is an acknowledged mode (AM) radio bearer.    -   Clause 22. The method of Clause 21, wherein the first radio link        control (RLC) entity and the second RLC entity are acknowledged        mode (AM) RLC entities.    -   Clause 23. The method of Clause 12, wherein the trigger for the        packet data convergence protocol (PDCP) retransmission indicates        a re-establishment of the PDCP entity.    -   Clause 24. The method of Clause 12, wherein the trigger occurs        in response to starting a handover procedure.    -   Clause 25. The method of Clause 24, wherein the handover        procedure is a dual active protocol stack (DAPS) handover.    -   Clause 26. The method of Clause 24, wherein the handover        procedure comprises uplink data switching.    -   Clause 27. The method of Clause 24, wherein:

the handover procedure comprises transmitting, by the base station (BS),a sequence number (SN) status transfer message to a target BS; and

the SN status transfer message comprises the first PDCP SN associatedwith the PDCP packet and the second PDCP SN associated with theduplicate of the PDCP packet.

-   -   Clause 28. The method of Clause 12, wherein the trigger is in        response to a PDCP data recovery procedure.    -   Clause 29. The method of Clause 12, wherein the first PDCPSN and        the second PDCP SN have respective fixed lengths that are either        twelve bits or eighteen bits.    -   Clause 30. The method of Clause 12, wherein:

the first PDCP SN is included in a first header of the first PDCPpacket; and

the second PDCP SN is included in a second header of the duplicate PDCPpacket.

-   -   Clause 31. The method of Clause 12, wherein retransmitting the        PDCP packet comprises at least one of:

retransmitting the first PDCP packet based on the first PDCP sequencenumber (SN); and

retransmitting the duplicate PDCP packet based on the second PDCP SN.

-   -   Clause 33. An apparatus for utilization in wireless        communications comprising:    -   an antenna for use in transmission of electromagnetic signals;    -   a memory for maintaining computer-readable code; and    -   a processor for executing the computer-readable code that causes        the apparatus to:

establish, at a central unit (CU), at least one packet data convergenceprotocol (PDCP) entity for a multicast radio bearer (MRB) associatedwith a first MBS service;

provide, by the PDCP entity, a first PDCP sequence number (SN)associated with a PDCP packet and further associated with a firstdistributed unit (DU) of the BS;

provide, by the PDCP entity, a second PDCP SN associated with aduplicate of the PDCP packet and further associated with a second DU ofthe BS; and

transmit at least one of the PDCP packet and the duplicate of the PDCPpacket based on the first PDCP SN and the second PDCP SN.

-   -   Clause 34. The apparatus of Clause 33, wherein the apparatus        establishes:

a first radio link control (RLC) entity for the PDCP packet transmittedvia the first distributed unit (DU); and

a second RLC entity for the duplicate of the PDCP packet transmitted viathe second DU.

-   -   Clause 35. The apparatus of Clause 34, wherein:

the first RLC entity is established at the first DU; and

the second RLC entity is established at the second DU.

-   -   Clause 36. The apparatus of Clause 34, wherein the at least one        PDCP entity is a single PDCP entity commonly established for the        first RLC entity and the second RLC entity.    -   Clause 37. The apparatus of Clause 34, wherein the at least one        PDCP entity comprises a first PDCP entity, established for the        first RLC entity, and a second PDCP entity, established for the        second RLC entity.    -   Clause 38. The apparatus of Clause 34, wherein the apparatus        establishes:

a first medium access control (MAC) entity, associated with the firstRLC entity, for transmission of a first MAC protocol data unit (PDU) viathe first DU; and

a second MAC entity, associated with the second RLC entity, fortransmission of a second MAC PDU via the second DU.

-   -   Clause 39. The apparatus of Clause 33, wherein the apparatus        establishes a data radio bearer (DRB) associated with the first        MBS service.    -   Clause 40. The apparatus of Clause 33, wherein in response to a        trigger for PDCP packet retransmission, the apparatus        retransmits at least one of the PDCP packet and the duplicate of        the PDCP packet based on the first PDCP SN and the second PDCP        SN.    -   Clause 42. The apparatus of Clause 40, wherein the trigger for        the PDCP retransmission indicates a re-establishment of the PDCP        entity.    -   Clause 43. The apparatus of Clause 40, wherein the trigger        occurs in response to starting a handover procedure.    -   Clause 44. The apparatus of Clause 40, wherein the trigger is in        response to a PDCP data recovery procedure.    -   Clause 45. An apparatus for utilization in wireless        communications comprising:    -   an antenna for use in transmission of electromagnetic signals;    -   a memory for maintaining computer-readable code; and    -   a processor for executing the computer-readable code that causes        the apparatus to:

establish at a central unit (CU), at least one packet data convergenceprotocol (PDCP) entity for a multicast radio bearer (MRB) associatedwith a first MBS service;

maintain, by the PDCP entity:

a first PDCP sequence number (SN) associated with a PDCP packettransmitted via a first distributed unit (DU) of the BS; and

a second PDCP SN associated with a duplicate of the PDCP packettransmitted via a second DU of the BS; and

in response to a trigger for PDCP packet retransmission, retransmit atleast one of the PDCP packet and the duplicate of the PDCP packet basedon the first PDCP SN and the second PDCP SN.

-   -   Clause 46. The apparatus of Clause 45, wherein the apparatus        establishes:

a first radio link control (RLC) entity for the PDCP packet transmittedvia the first DU; and

a second RLC entity for the duplicate of the PDCP packet transmitted viathe second DU.

-   -   Clause 47. The apparatus of Clause 46, wherein:

the RLC entity is established at the first DU; and

the second RLC entity is established at the second DU.

-   -   Clause 48. The apparatus of Clause 46, wherein the at least one        PDCP entity is a single PDCP entity commonly established for the        first RLC entity and the second RLC entity.    -   Clause 49. The apparatus of Clause 46, wherein the at least one        PDCP entity comprises a first PDCP entity, established for the        first RLC entity, and a second PDCP entity, established for the        second RLC entity.    -   Clause 50. The apparatus of Clause 46, wherein the apparatus        establishes:

a first medium access control (MAC) entity, associated with the firstradio link control (RLC) entity, for transmission of a first MACprotocol data unit (PDU) via the first distributed unit (DU); and

a second MAC entity, associated with the second RLC entity, fortransmission of a second MAC PDU via the second DU.

-   -   Clause 51. The apparatus of Clause 45, wherein the apparatus        establishes a data radio bearer (DRB) associated with the first        MBS service.    -   Clause 52. The apparatus of Clause 45, wherein the apparatus        generates the duplicate of the PDCP packet utilizing a PDCP        duplication process.    -   Clause 53. The apparatus of Clause 52, wherein an internet        protocol (IP) packet, associated with the MRB, is duplicated by        the PDCP duplication process to generate the first PDCP packet        and the duplicate PDCP packet.    -   Clause 54. The apparatus of Clause 45, wherein the multicast        radio bearer (MRB) is an acknowledged mode (AM) radio bearer.    -   Clause 55. The apparatus of Clause 54, wherein the first radio        link control (RLC) entity and the second RLC entity are        acknowledged mode (AM) RLC entities.    -   Clause 56. The apparatus of Clause 45, wherein the trigger for        the packet data convergence protocol (PDCP) retransmission        indicates a re-establishment of the PDCP entity.    -   Clause 57. The apparatus of Clause 45, wherein the trigger        occurs in response to starting a handover procedure.    -   Clause 58. The apparatus of Clause 57, wherein the handover        procedure is a dual active protocol stack (DAPS) handover.    -   Clause 59. The apparatus of Clause 57, wherein the handover        procedure comprises uplink data switching.    -   Clause 60. The apparatus of Clause 57, wherein:

the handover procedure comprises transmitting, by the base station (BS),a sequence number (SN) status transfer message to a target BS; and

the SN status transfer message comprises the first PDCP SN associatedwith the PDCP packet and the second PDCP SN associated with theduplicate of the PDCP packet.

-   -   Clause 61. The apparatus of Clause 47, wherein the trigger is in        response to a PDCP data recovery procedure.    -   Clause 62. The apparatus of Clause 45, wherein the first PDCPSN        and the second PDCP SN have respective fixed lengths that are        either twelve bits or eighteen bits.    -   Clause 63. The apparatus of Clause 45, wherein:

the first PDCP SN is included in a first header of the first PDCPpacket; and

the second PDCP SN is included in a second header of the duplicate PDCPpacket.

-   -   Clause 64. The apparatus of Clause 45, wherein retransmitting        the PDCP packet comprises at least one of:

retransmitting the first PDCP packet based on the first PDCP sequencenumber (SN); and

retransmitting the duplicate PDCP packet based on the second PDCP SN.

-   -   Clause 65. A method of multicast broadcast service (MBS) data        transmission, comprising:

receiving, by a user equipment (UE) from a base station (BS),configuration parameters of a multicast radio bearer (MRB) associatedwith a first MBS service, wherein the BS comprises a central unit (CU),a first distributed unit (DU) and a second DU; and

receiving, by the UE from the first DU, a transport block associatedwith the MRB, wherein

the first transport block comprises a packet data convergence protocol(PDCP) packet and wherein

the first DU receives the PDCP packet from a PDCP entity, established inthe CU of the BS, via a first interface;

the second DU receives a duplicate of the PDCP packet from the PDCPentity via a second interface; and

the duplicate of the PDCP packet is transmitted via the second DU.

-   -   Clause 66. The method of Clause 65, wherein

a first radio link control (RLC) entity is established in the firstdistributed unit (DU) for transmission of the packet data convergenceprotocol (PDCP) packet; and

a second RLC entity is established in the second DU for transmission ofthe duplicate of the PDCP packet.

-   -   Clause 67. The method of Clause 66, wherein the packet data        convergence protocol (PDCP) entity is commonly established for        the first radio link control (RLC) entity and the second RLC        entity.    -   Clause 68. The method of Clause 65 further comprising receiving        a second transport block, comprising the duplicate of the packet        data convergence protocol (PDCP) packet, from the second        distributed unit (DU).    -   Clause 69. The method of Clause 68 further comprising decoding        the first transport block and the second transport block for        enhancing reliability of reception of the first multicast        broadcast service (MBS).    -   Clause 70. The method of Clause 68, wherein the packet data        convergence protocol (PDCP) entity utilizes a packet duplication        process to generate the duplicate of the PDCP packet.    -   Clause 71. The method of Clause 1, further comprising receiving        a packet data convergence protocol (PDCP) packet duplication        activation signaling indicating activation of PDCP packet        duplication for the multicast radio bearer (MRB).

The invention claimed is:
 1. A method of multicast broadcast service (MBS) data transmission comprising: establishing, by a base station (BS) at a central unit (CU) of the BS, at least one packet data convergence protocol (PDCP) entity for a multicast radio bearer (MRB) associated with a first MBS service; providing, by the PDCP entity, a first PDCP sequence number (SN) associated with a PDCP packet and further associated with a first distributed unit (DU) of the BS; providing, by the PDCP entity, a second PDCP SN associated with a duplicate of the PDCP packet and further associated with a second DU of the BS; and transmitting, by the BS, at least one of the PDCP packet and the duplicate of the PDCP packet based on the first PDCP SN and the second PDCP SN.
 2. The method of claim 1 further comprising establishing by the BS: a first radio link control (RLC) entity for the PDCP packet transmitted via the first distributed unit (DU); and a second RLC entity for the duplicate of the PDCP packet transmitted via the second DU.
 3. The method of claim 2, wherein: the first RLC entity is established at the first DU of the BS; and the second RLC entity is established at the second DU of the BS.
 4. The method of claim 2, wherein the at least one PDCP entity is a single PDCP entity commonly established for the first RLC entity and the second RLC entity.
 5. The method of claim 2, wherein the at least one PDCP entity comprises a first PDCP entity, established for the first RLC entity, and a second PDCP entity, established for the second RLC entity.
 6. The method of claim 2 further comprising establishing: a first medium access control (MAC) entity, associated with the first RLC entity, for transmission of a first MAC protocol data unit (PDU) via the first DU; and a second MAC entity, associated with the second RLC entity, for transmission of a second MAC PDU via the second DU.
 7. The method of claim 1 further comprising establishing a data radio bearer (DRB) associated with the first MBS service.
 8. The method of claim 1 further comprising in response to a trigger for PDCP packet retransmission, retransmitting, by the BS, at least one of the PDCP packet and the duplicate of the PDCP packet based on the first PDCP SN and the second PDCP SN.
 9. The method of claim 8, wherein the trigger for the PDCP retransmission indicates a re-establishment of the PDCP entity.
 10. The method of claim 8, wherein the trigger occurs in response to starting a handover procedure.
 11. The method of claim 8, wherein the trigger is in response to a PDCP data recovery procedure.
 12. A method of multicast broadcast service (MBS) data transmission, comprising: establishing, by a base station (BS) at a central unit (CU) of the BS, at least one packet data convergence protocol (PDCP) entity for a multicast radio bearer (MRB) associated with a first MBS service; maintaining, by the PDCP entity: a first PDCP sequence number (SN) associated with a PDCP packet transmitted via a first distributed unit (DU) of the BS; and a second PDCP SN associated with a duplicate of the PDCP packet transmitted via a second DU of the BS; and in response to a trigger for PDCP packet retransmission, retransmitting, by the BS, at least one of the PDCP packet and the duplicate of the PDCP packet based on the first PDCP SN and the second PDCP SN.
 13. The method of claim 12 further comprising establishing by the base station: a first radio link control (RLC) entity for the PDCP packet transmitted via the first DU; and a second RLC entity for the duplicate of the PDCP packet transmitted via the second DU.
 14. The method of claim 13, wherein: the RLC entity is established at the first DU of the BS; and the second RLC entity is established at the second DU of the BS.
 15. The method of claim 13, wherein the at least one PDCP entity is a single PDCP entity commonly established for the first RLC entity and the second RLC entity.
 16. The method of claim 13, wherein the at least one PDCP entity comprises a first PDCP entity, established for the first RLC entity, and a second PDCP entity, established for the second RLC entity.
 17. The method of claim 13 further comprising establishing: a first medium access control (MAC) entity, associated with the first radio link control (RLC) entity, for transmission of a first MAC protocol data unit (PDU) via the first distributed unit (DU); and a second MAC entity, associated with the second RLC entity, for transmission of a second MAC PDU via the second DU.
 18. The method of claim 12 further comprising establishing a data radio bearer (DRB) associated with the first MBS service.
 19. The method of claim 12 further comprising generating, by the PDCP entity, the duplicate of the PDCP packet utilizing a PDCP duplication process.
 20. The method of claim 19, wherein an internet protocol (IP) packet, associated with the MRB, is duplicated by the PDCP duplication process to generate the first PDCP packet and the duplicate PDCP packet.
 21. The method of claim 12, wherein the multicast radio bearer (MRB) is an acknowledged mode (AM) radio bearer.
 22. The method of claim 21, wherein the first radio link control (RLC) entity and the second RLC entity are acknowledged mode (AM) RLC entities.
 23. The method of claim 12, wherein the trigger for the packet data convergence protocol (PDCP) retransmission indicates a re-establishment of the PDCP entity.
 24. The method of claim 12, wherein the trigger occurs in response to starting a handover procedure.
 25. The method of claim 24, wherein the handover procedure is a dual active protocol stack (DAPS) handover.
 26. The method of claim 24, wherein the handover procedure comprises uplink data switching.
 27. The method of claim 24, wherein: the handover procedure comprises transmitting, by the base station (BS), a sequence number (SN) status transfer message to a target BS; and the SN status transfer message comprises the first PDCP SN associated with the PDCP packet and the second PDCP SN associated with the duplicate of the PDCP packet.
 28. The method of claim 12, wherein the trigger is in response to a PDCP data recovery procedure.
 29. The method of claim 12, wherein the first PDCPSN and the second PDCP SN have respective fixed lengths that are either twelve bits or eighteen bits.
 30. The method of claim 12, wherein: the first PDCP SN is included in a first header of the first PDCP packet; and the second PDCP SN is included in a second header of the duplicate PDCP packet.
 31. The method of claim 12, wherein retransmitting the PDCP packet comprises at least one of: retransmitting the first PDCP packet based on the first PDCP sequence number (SN); and retransmitting the duplicate PDCP packet based on the second PDCP SN. 